With r22s words of caution, say it loud and clear that you don't want any retribution, just a fighting chance.
Only God knows what he's thinking now. It just really seems like he's doing what I've wanted to do so many times in the past 6 months - cut and run. I've screwed up (as has my W) and there are differences/issues that aren't going away anytime soon. It is sooo easy to think I've hurt her and I too much and running away will feel great.
Tell him & help him feel that his past failures are really successes - they helped you and him get to deep issues that make boys into men. The pain of the past is gone, and the future awaits.
Ask for the chance, don't hint. He may say no. He may have papers ready. It doesn't matter. Take the chance.
Remember - this is just my POV, but you are running your life. Choose after thought for what is right, not who is right.
