Sorry you are here, but you've come to a good place. First off, it's best to start your own thread so all of your history will be in one place.
To answer some of your questions: yes, your situation is relatively common. Spouses have left and the actions of the left behind spouse (LBS) have had an impact, positive or negative, on whether the walk away spouse (WAS) has returned or not. If you have not read Divorce Busting (DB) or Divorce Remedy (DR), please do so ASAP. The first thing you should do is stop all pursuit. Stop pleading, stop begging and focus on you. If you accept that you have no control over the outcome of the situation and choose to love yourself and build yourself up instead of tearing your hair out and trying to convince your WAS to return, you will be much more likely to succeed.
The fact that you are fighting still shows that you are in a state of conflict, which is a good sign as it shows you both still care about the relationship. Be careful though, because you are creating history in the present, and you would be better served by creating positive memories than negative ones.
I think this friendship he has is in fact an emotional affair (EA) and this alters the dynamic of your situation considerably. You will find quite a lot of information here about what you can do, but remember that you have to be committed and brave enough to face your own demons, because that's where you're able to do the most effective work.
All is not lost. There's a great deal of potential. Read the books and come here for support and discussion.
“No problem can be solved from the same level of consciousness that created it. ” – Albert Einstein
