Just my quick thoughts:
For your rank, I think you played a perfectly respectable opening. If you can put this much thought and planning into your moves, I'm sure you'll be improving soon.
6: With regards to the high versus low debate, I see it this way: the stone on the fourth line obviously has more territory potential, and puts more pressure on the black approach. So, in my mind, you want to play high when you can afford it. The deciding factor for whether or not you can afford it is this: if black approaches around M17, it threatens to undercut and your corner will be under pressure. If you have enough support on the top, black cannot safely play M17, so your high stone is safe.
- Click Here To Show Diagram Code
[go]$$B Does this threaten black enough?
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$$ | . . . . . . . . . 8 . 7 . . . . . . . |
$$ | . . . 2 . . . . . , . . . 6 . 4 . . . |
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$$ | . . . . . . . . . . . . . . . . 5 . . |
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$$ | . . . , . . . . . , . . . . . 1 . . . |
$$ | . . . . 3 . . . . . . . . . . . . . . |
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7 here likely would not be played immediately, but it is a major weakness of the shape created by the high stone. If you feel like you can handle black getting the approach there, then by all means play high. You are correct, playing high here is better than it would be if the top left corner was white's, as it works together better. Personally, I am perhaps too afraid of the black approach, so I don't play high often. However, it's totally playable and in this situation I feel that it's more a matter of taste.
As far as your second question for this move, if black had swapped S16 for R17, he would have a portion of the corner, with the stability it brings, at the expense of giving you the other half. The reason to do this (from black's perspective) is to leave the corner invasion open for later. If black's group is safe and stable, it may be worth leaving the corner available to get extra points. However, this is only if he can invade without causing it to hurt his other stones too much, and it comes at the risk that eventually you will seal off the corner entirely.
- Click Here To Show Diagram Code
[go]$$B Personally, if I feel like leaving the corner open as B, I try to play lightly like this.
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$$ | . . . 2 . . . . . , . . . 6 . 4 . . . |
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$$ | . . . . . . . . . . . . . . . . 5 . . |
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$$ | . . . , . . . . . , . . . . . 7 . . . |
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$$ | . . . , . . . . . , . . . . . 1 . . . |
$$ | . . . . 3 . . . . . . . . . . . . . . |
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$$ ---------------------------------------[/go]
10: I never like approaching 5-3 stones, I don't really know how to handle them either =/
12: If you want to separate black, you may want to consider doing it directly, around D5. It forces black to defend one side, but allows you to put some pressure on the other, as well as not getting closed in.
24: A good general idea of direction, but you might want to consider 11. It's low, so it's harder to undercut, but it has a safe extension in either direction, so you cannot get cut off.
31: Bad for black. As you pointed out, he let you out too easily. Making that tiger's mouth is a good shape point that tends to be good for you when available. For that reason, P4 is big for both sides.
36: As it buys safety for your group, this move is fine. Black got little, but forced you to stabilize your group further.