The most important thing is what is best for you and your sons. I guess I haven't gotten the impression that your ex has given any big hints that he is interested in working things out. Maybe it's anecdotal, but guys that are interested at least make some effort to establish contact, even if it's just calling to talk to the kids and keeping you on the line for part of the time.
So about Michigan. I think you should choose that if it's best for you and for your kids. Somewhere much lower on the list would be solely to be closer to ex. Think of it this way....if despite moving closer to him nothing ever develops would you regret the decision and say to yourself "I should have went somewhere else". If you still say..."I want to be in MI even if my R with ex is truly over." then I think you might be closer to answering your question.
From my standpoint, I've already indicated, and I stick by it, that I will not leave this job and my kids behind for the sake of my ex. Would I ever move for her? Possibly if we were back together. Anything less is just sacrificing my wants and needs solely for a potential R with her. I would think less of myself and she would think less of me also.
Oh, about the R talk. Who says you can't? You have a difficult life decision and it involves your ex's son. Ask his opinion. Guys like thinking you respect their judgement. Tell him of the jobs you are considering and ask if he has input in the location. Go around the issue of asking him whether you guys even have a chance. Let him tell you indirectly if he'd prefer you were closer.
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt
