He sounds unstable.
I know this will be hard to believe but you, on the other hand, sound like you're in a fantastic place because you have acceptance.
He is who he is. So be it
. Perfect. You can't control or change him, but you can protect yourself and your son-first and foremost financially.
Each state has different laws regarding divorce and marital infidelity. Do a google to see if infidelity can be used as a means of divorce.
Please don't think of yourself as not having resources. You do, you just have to fight for them.
Please don't let him know that you know about the affair and
go see an attorney ASAP to learn about your options. I know it's hard to imagine, but my advice is to shift into survival mode because your husband is a bit nuts right now. He's caught in the throes of an affair and will likely be a bit crazy for awhile. Mine did horrible things, horrible, that he now regrets but it took two years for him to recognize what he had really done with that woman he told me he was in love with-he cheated himself.
*Lots of lawyers will do a free consultation with you over the phone.
*Start packing official forms-tax forms, birth certificate, etc. Everything you will need to protect yourself and your son.
*A lawyer will tell you what to do about your bank accounts, etc. In my first divorce, my husband withdrew every penny out of the savings and checking accounts before he told me we were getting divorced. It was perfectly legal.
*Do not call his family members for support. Blood is blood.
I do hope you're doing all right. It sounds like he's torturing you. It often helped me when fighting with my AH to focus on my kids. Go hang out with them, let them know I love them.