At move 66, I would have connected with P8. Initially it looks like gote. Even then, it is a good gote because it connects one maybe alive group and one probably alive group.
Doing so removes many ko threats and kakaris against you. It allows you many more options in the future.
However, it would be good if you could avoid having to make decisions like that. Your group got heavy very fast. I think that you would do better to play more lightly in such situations. Let's look at a lighter alternative a few moves back.
My understanding of a move like P18 is that it is a probe. It asks the opponent which he values more: the side or the corner. If he plays R17 or Q17 or Q18, he is answering that he likes the corner more. If he replies as he did, he is telling you that he likes the side more.
Given that information, you nonetheless chose to invade the side, and a rather deep invasion at that. It is not surprising that you got into a difficult game.
I would have reduced rather than invaded. If he really wants the upper side, concede it, but keep him low. Save the aji of the P18 stone for a future corner invasion starting with 'a'.
- Click Here To Show Diagram Code
[go]$$W
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . 1 a . . . |
$$ | . . O O X . . . . . . . . . 2 . . . . |
$$ | . . O X . . . . . X . . . . . X . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . 3 . . . . . . X . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . b . . |
$$ | . . . . . . . . . . . . . . . . c . . |
$$ | . . . O . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . X . , . . . . . X . O . |
$$ | . . O . . X . . . . . . . X . . X . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
In the above diagram,

is safe because it has plenty of room to run southward if needed. Your

is light, and eventually he has to play one more move near it - in gote! - to ensure that it doesn't cause trouble.
Another effect of the aji of

is that 'b' is now sente for you, but if he plays there first, 'c' is gote for him.
Someone will probably tell you that LZ says play 'a' immediately. That strikes me as rather vulgar. LZ really likes corner invasions - maybe too much.
Given the black wall at E17/D14, a lighter, more flexible, and more influential move seems best.