Sure - short summary: I let my girls and their step Dad, my RAH, determine their own relationship and only watched from the periphery. Now, that said, he is 16 months sober and in AA, and we remain married although we still live separately.
My thinking was that the girls (at the time, 13 and 17) needed to decide what they were comfortable with and my RAH needed to decide what his priorities were as well. And I realized I was being controlling with it all - trying to "manage" everything when it really was none of my business. When I stepped out of the way, he has been able to take more of a lead and they have been much more receptive and have a good relationship with him on their own terms and he remains a good influence on them.
My RAH and I get along GREAT living separately. Having separate finances. Separate time schedules. We still have conflict, but the space has been so incredibly beneficial for both our recoveries that I have no regrets for making the choices I made. Maybe doing things incrementally here is a good option for you too. Having the BF move back to town, only to his own place and taking it slow. And encouraging him to have a relationship with your son on terms that work for both of them and one that is outside of your relationship with him.
When my time is right to have a "family" again in the traditional sense, I will know it. And I am in no rush as right now, taking it all slow works great for me, my girls, and my RAH.