Here's the condensed version: Wow, that whole situation, on both sides, sounds hurtful, but couples have recovered from worse. So can you guys, if you both want it.

Get some help, a therapist for yourself first to help with your depression and the problems of unrealistic expectations. And if you want to make a go with the girl, a couples counselor for both of you. One of the things you might work on with the therapist are concepts of trust, honesty and what's cheating and what's not. Those issues sound all muddled up in this relationship.

I wish you the best. I've known couples to recover from worse situations and to end up happy being together. But it took a lot of work from both partners. Good Luck!