Hello feelingdown93,
I am also a gay man in my 20s and I would like to offer you my perspective on the things that trouble you.
These memories that you describe.. seem very sweet and tender. They are a part of your sexual awakening and you should really look back to them with warmth and fondness, not condenm them! I understand that you feel awkward because at the time your friend was 10 years old, but this doesn't really mean anything.. You were a kid yourself too (14 is not exactly adult), naturally attracted to boys close to your age and when the occasion arose something else arose too

There is nothing in your narration that even remotely suggests manipulation or impulsivity.. You clearly tried to gain from the situation as much as you could (which was totally natural by the way), WITHOUT trespassing on your friend. You leaned on his shoulder and tried to make it look as natural as possible in order not to disturb him. 10 year old boys are not famous for their tact: if you made him uncomfortable he would complain and shoo you away without second thoughts. Even if he didn't do that, that kind of physical contact could hardly classify as molestation or trauma! I also feel that if he showed the faintest signs of irritation you would be the first one to notice and keep your distances!
[Just to be sure here manipulation or impulsivity would mean luring him alone in a nearby room and having your way with him whether he wanted it or not. I mean it is a totally different situation! Even if the thought DID occur to you, it still wouldn't matter: control always excites us, but fantasizing is entirely different than acting.]
I am so sorry that you feel so bad for such a trivial thing, but it is really not worth it.. If I may express an entirely personal opinion, I believe people with OCD have so many strict rules and preconceptions about sexuality that lead them to fear their sexuality and restrain/punish themselves (that surely happened to me!). We are not robots you know.. we cannot choose at will what excites us and what not! But it is a real shame that this guilt keeps you closed to yourself, your sexuality dormant and doesn't let you connect with another person

Our life is very short to fret over such things and time won't reverse, in a few years you will probably regret the time you spent worrying about all these stuff (but one could always argue that you needed that time to reach that conclusion

)
I became instantly fond of you, because in many ways you remind me of myself.. I truly hope you will give yourself some slack, that will alleviate your worries.