Hi EM - At least you are in there doing what you have to do. I don't understand why the W would blame you for the son's acting out, but a lot of MLC behavior does not make any sense from a logical standpoint.
As far as OM requiring surgery, your W breaking off the R with him had nothing to do with his health problems. For her to think so only demonstrates more warped thinking on her part. I guess I don't have to tell you that.
I don't know what to advise but it appears that your patience is being tested here. I hope you get the strength to roll with the punches and not get too down. After all she is still with you, not with that loser. I guess it is tough to quit cold turkey on a relationship. She must have gone with the same thing with you while she was involved with him (guilt and memories bearing down on her). I know it is going to take some time for the trust to build and for her to let this guy go completely. Still, I am hoping for the best. Perhaps you guys can do out and do something special this weekend and enjoy each other's company.
What is your opinion of the MC and the advice he is giving?