Definitely don't isolate yourself in this time. That's what the enemy wants. Alone you're an easy target. Band together! You have brothers here who will stand with you.
Don't give up on your marriage. Yes you made a wrong choice, but don't let that be the reason you decide to give up now. You pointed out how far you've come, fight for that, and fight for your marriage.
Do the hard thing, and open up as much communication with your wife as you can. Ask her what she needs from you. Do what you have to save it, if after you've done everything you can, she still wants out, that's her choice then, but then you can rest in the fact that despite past mistakes, you did all you can.
I know you want God's will for your life, well brother, one of the things God makes clear is that He hates divorce. His will is for you to fight for it. You can't make her stick around, but you do your part.
All this crap hurts and when everything else seems to be falling apart around us at the same time it's even harder, but you can do it. You can do all things!
Remember, God has called you. Those He called He has sanctified and those He has sanctified, He has justified. You feel unworthy, but He calls you beloved son.
Fight the good fight, and don't give up.