Havn't read threw the whole thread, but from your posts I understand the situation.
I always read but rarelly post, anyways:
If it makes you feel any better, i went threw a similar event. Decided to change my life around and go at life the right way, start university etc and my 4 year relationship went down the shitter.
Next day my boys call me and tell me the ''wife'' (not married but moved in, pretty much common law) is out with some fag, fucking at some party. Never saw that one comming. Sucks to think how shit can get so fucked up.
Anyways at first I didn't even know how I could handle it and it definatelly put me down for a while.
Never thought shit was going to get better etc. But its been a long time and now im 10 time happier then i ever was with her.
Some things are for the best bro, I'm sure things will work out, you seem like a really good guy.
Keep your head up, and don't put yourself down because of someone else's descision, when it comes down to it your the good guy and good things will come your way,
-Eric