I'm going to go ahead and just say it, your husband has absolutely no boundaries. He had an affair years ago and I don't see where he ever received any kind of therapy or established what was broken in him to do such a thing. He has MAJOR mommy issues and still appears to have crap boundaries and now has a pseudo-girlfriend dynamic with his biological mother. There is a little understood issue called Genetic Sexual Attraction and there has been minimal studies done. There appears to be a problem (it's rare but occurs) with reunions of family member separated by adoption (or in this case, abandonment.) This relationship is WRONG, it doesn't matter that it is his mother, it's wrong. I don't think there was anything you did or didn't do to push him into this bizarre dynamic. Rather I see him rewriting a marriage to fit and excuse this really inappropriate situation with his mother.
While I believe in DBing I don't think MWD ever imagined that the OW would be a WS parent! Her husband seems to be projecting BIG TIME onto InLove42 by spying on her, stating she is "out partying with guys" and overall being abusive and controlling to her. I do think IL42 needs to put strong boundaries into place, call a spade a spade and tell her husband she can be the only "spouse" relationship if she plans to stay married to him. It is very squicky that he STAYS overnight with his bio-mom in place of his wife. IL42, take what works and throw out the rest. Your husband became nervous and upset when you appeared to be moving on? I say continue to GAL and move on. He needs a HUGE wake-up call before he slips past a line he cannot uncross again. Stop telling him you want to "work on the marriage" instead let him know that you love him and will prove it by giving him what he wants, a divorce. After that, go completely dark and seriously fill up your time with Salsa dancing, be with supportive friends, and take up hobbies that keep you out of the camera ridden home as much as possible. You have the potential of turning this thing around but it requires a lot of counter-intuitive moves. There are no kids to force contact so make yourself mysterious and elusive.
M 10yrs T 13yrs BD #1Oct 2015-PA between WAH and COW BD #2 April 2016-WH resumed PA, she broke it off Jan 2 2017 WH says he wants divorce April '17-Letting go 2018 D busted DD8, DS6, DS3