I also have difficulties with those "open border"/undefined eye-shape problems. I try to cope with this in two ways: First is starting not with vital points but with eye-space-reducing-moves and submissive replys (if they work I don't need to read complicated stuff). This is simple and can be calculated quite quickly. Second is following the proverb that your opponent's key point is your own.
Disclaimer: I did need a board and stones again, to figure out all the intricacies. Though I have to say, I got to the first four moves on my own and saw a good chunk of the variations.
$$Wc Reducing Black's eye-space
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . . , X O . .
$$ | . . . X . O . .
$$ | . X 1 O O . . .
$$ | . . . . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Wc Reducing Black's eye-space
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . . , X O . .
$$ | . . . X . O . .
$$ | . X 1 O O . . .
$$ | . . . . . . . .
$$ +-----------------[/go]
$$Wc Variation 1: Tearing through
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . . , X O . .
$$ | . . 3 X . O . .
$$ | . X 1 O O . . .
$$ | . 2 . . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Wc Variation 1: Tearing through
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . . , X O . .
$$ | . . 3 X . O . .
$$ | . X 1 O O . . .
$$ | . 2 . . . . . .
$$ +-----------------[/go]
$$Wc Variation 2: Helping Black build a nice nest
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . 5 X X . O . .
$$ | X 6 . , X O . .
$$ | . . 2 X . O . .
$$ | 4 X 1 O O . . .
$$ | . 3 . . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Wc Variation 2: Helping Black build a nice nest
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . 5 X X . O . .
$$ | X 6 . , X O . .
$$ | . . 2 X . O . .
$$ | 4 X 1 O O . . .
$$ | . 3 . . . . . .
$$ +-----------------[/go]
Now you can start going backward. Try

at

for example. It still lives (insert effortful practice ; )), so you have to go back even further.
$$Wc Variation 3: where are Black's eyes?
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . d a X O . .
$$ | b c 2 X . O . .
$$ | . X 1 O O . . .
$$ | . . . . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Wc Variation 3: where are Black's eyes?
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . d a X O . .
$$ | b c 2 X . O . .
$$ | . X 1 O O . . .
$$ | . . . . . . . .
$$ +-----------------[/go]
It's time to go deeper now. Recognise the eye-shape, see familair patterns. After the exchange

for

, it is "easy" to see that 'a' is already an eye. The second eye will most likely be around 'b'. Do you have any moves to take away the second eye?
I reckon you will end up in situations where 'c' and 'd' become miai and so Black lives.
With all that out of the way: What did we learn?
1) We have an idea, where Black's eyes will be.
2) When Black responds at

he's already alive.
So

seems to be a key point in Black's shape. According to proverb this key point could also work in White's favour!
$$Wc Variation 4: Cutting the eye!
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . . . X O . .
$$ | . . 1 X . O . .
$$ | . X . O O . . .
$$ | . . . . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Wc Variation 4: Cutting the eye!
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . . . X O . .
$$ | . . 1 X . O . .
$$ | . X . O O . . .
$$ | . . . . . . . .
$$ +-----------------[/go]
$$Wc Variation 4: tearing through the 2nd
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . . . X O . .
$$ | . 2 1 X . O . .
$$ | . X 3 O O . . .
$$ | . . . . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Wc Variation 4: tearing through the 2nd
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . . . X O . .
$$ | . 2 1 X . O . .
$$ | . X 3 O O . . .
$$ | . . . . . . . .
$$ +-----------------[/go]
$$Wc Variation 5: Entering the belly of the beast
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X b O . .
$$ | X . . . X O . .
$$ | . . 1 X a O . .
$$ | . X 2 O O . . .
$$ | . . . . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Wc Variation 5: Entering the belly of the beast
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X b O . .
$$ | X . . . X O . .
$$ | . . 1 X a O . .
$$ | . X 2 O O . . .
$$ | . . . . . . . .
$$ +-----------------[/go]
This gets more complex but can also be made a little bit rational. White should not be so fast and play atari at 'a'. Black will sacrifice this stone and live - please confirm : )
Furthermore when Black cannot capture White with his next move, the atari can be played later as well. If Black plays 'a', White can force 'b' with the same result.
$$Wc Variation 5
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . . . X O . .
$$ | . 3 1 X . O . .
$$ | . X 2 O O . . .
$$ | . . . . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Wc Variation 5
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . . . X O . .
$$ | . 3 1 X . O . .
$$ | . X 2 O O . . .
$$ | . . . . . . . .
$$ +-----------------[/go]
So, when you have confirmed that

is Black's key point to live when White decides to atari right away, why not play there yourself?
$$Bcm4 Variation 5: No ko!
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X 4 O . .
$$ | X . 3 . X O . .
$$ | . O O X 2 O . .
$$ | 1 X X O O . . .
$$ | . . . . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Bcm4 Variation 5: No ko!
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X 4 O . .
$$ | X . 3 . X O . .
$$ | . O O X 2 O . .
$$ | 1 X X O O . . .
$$ | . . . . . . . .
$$ +-----------------[/go]
$$Bcm4 Variation 6: Black collapses due to liberty shortage
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X 8 . 3 X O . .
$$ | 6 O O X 2 O . .
$$ | 1 X X O O . . .
$$ | . 5 4 7 . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Bcm4 Variation 6: Black collapses due to liberty shortage
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X 8 . 3 X O . .
$$ | 6 O O X 2 O . .
$$ | 1 X X O O . . .
$$ | . 5 4 7 . . . .
$$ +-----------------[/go]
$$Bcm4 Variation 7: Ko
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . 3 4 X O . .
$$ | 1 O O X 2 O . .
$$ | . X X O O . . .
$$ | . . . . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Bcm4 Variation 7: Ko
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . 3 4 X O . .
$$ | 1 O O X 2 O . .
$$ | . X X O O . . .
$$ | . . . . . . . .
$$ +-----------------[/go]
$$Bcm4 Variation 8: If Black refuses the ko...
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X 8 . 3 X O . .
$$ | 1 O O X 2 O . .
$$ | 6 X X O O . . .
$$ | . 5 4 7 . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Bcm4 Variation 8: If Black refuses the ko...
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X 8 . 3 X O . .
$$ | 1 O O X 2 O . .
$$ | 6 X X O O . . .
$$ | . 5 4 7 . . . .
$$ +-----------------[/go]
But did you remember the proverb? Your opponent's key-point is your own?
$$Bcm4 Variation 9: Guzumi!
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . . . X O . .
$$ | . O O X . O . .
$$ | . X X O O . . .
$$ | . . 1 . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Bcm4 Variation 9: Guzumi!
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . . . X O . .
$$ | . O O X . O . .
$$ | . X X O O . . .
$$ | . . 1 . . . . .
$$ +-----------------[/go]
$$Bcm4 Variation 9: Or not...
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X 4 . . X O . .
$$ | 3 O O X . O . .
$$ | 2 X X O O . . .
$$ | . . 1 . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Bcm4 Variation 9: Or not...
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X 4 . . X O . .
$$ | 3 O O X . O . .
$$ | 2 X X O O . . .
$$ | . . 1 . . . . .
$$ +-----------------[/go]
So, I guess it's ko?
To be fair, this ko is better for Black:
$$Bcm4 Variation 10: Ko²
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . 1 3 X O . .
$$ | . O O X 2 O . .
$$ | 6 X X O O . . .
$$ | 7 4 5 . . . . .
$$ +-----------------
- Click Here To Show Diagram Code
[go]$$Bcm4 Variation 10: Ko²
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . O O O O . . .
$$ | . . X X . O . .
$$ | X . 1 3 X O . .
$$ | . O O X 2 O . .
$$ | 6 X X O O . . .
$$ | 7 4 5 . . . . .
$$ +-----------------[/go]
(I'm really tired now, so the possibilitiy is high that I missed something ^^)