Just be friends with your H. Neither you nor your H can compare to OP. You can both always find someone who you feel more chemistry. Heck, OM may end up a bummer over time (he already sounds a little controlling, selfish and pissy from what you've described), and someone better might show up after that. I've watched my D friends go through that situation. You sound like someone who is trying to be logical. You are just all s@rewed up by those hormones and endorphins. But gosh they do feel good!
I think the more important thing to do is to consider if your child is the kind of kid who can handle changes in his life well. Is he the kind of kid who will have no problem having two homes he moves between, two different sets of parents and families? Would he handle sharing one or more parents with step-siblings? I don't know if OM has kids, but your H may remarry or live with someone who has kids. Is your son the kind of kid who will handle this easily? If so, then you might as well concentrate on your own needs and wants and do what you want, otherwise I think if you love your child and care about his mental development and stability you shouldn't put him through this. Wait till he's older and then leave the marriage.
Otherwise, if he is a sensitive kid and you put him through having to deal with a situation he isn't emotionally equipped to handle, any relationship or marriage you have will eventually be affected by an unhappy child/teenager who will just make everyone's life kind of nightmarish (not that teens and kids have problems anyway, I just think it can be worse when you don't have good family structure and support). If OM is meant to be the one he will still be there later. If not, he's not meant to be. He didn't really love you anyway.
There is no arriving, ever. It is all a continual becoming.
