I can't do this anymore

I've been reading everyone's posts for a while, so thank you all for helping me to feel less alone.  I really need to tell someone what is happening as I cannot tell anyone I know. My husband is ADHD, has been since he was a kid but his parents chose to take him off medication. He was rediagnosed three years ago and I read everything I could on the subject. He wasn't interested in learning, wouldn't even let me speak about it, and just took the 30mg of Adderall and an anti-depressant that his GP gave him. I said for years that his medication was wrong. It finally took my telling him in August that if he didn't take the reins and get this under control, I was divorcing him. This is the only time that I have said that, although he has threatened divorce for 11 years, which I now realize he does to give his brain stimulation. He picked a therapist completely based on her looks (he proudly showed me a photo of her) which I didn't mind because at least he was going to one, but she knows absolutely NOTHING about ADHD. She has him talking about Mars/Venus communication issues, and has no clue about ADHD. I've read every marriage self help book in 17 years and it was only when I learned about ADHD that everything made complete sense. Luckily she referred him to a psychiatrist to deal with his medication, but he is currently off all meds. Was supposed to wean and re-evaluate, but instead he decided to go cold turkey. His therapist was completely charmed by him, and he can talk for hours about nothing. He would rehash every appointment with me as soon as he left. One time they spent 20 minutes of his session talking about her dog. She would laugh at his "antics" - like his new hobby of stealing street signs and the fact that it bothered me that he handed me his ipad to order him a fake vagina sex toy, as we were lying in bed not having sex. His sex drive totally disappeared when he was on meds, but he said "It's not a problem for me" when I tried to discuss that he needed to change his medication.

He came home from a trip this weekend and said he wanted a divorce (for the second time in 2017). I want to divorce him too, but we have children so I'm trying to handle it carefully. He seemed to be waiting for me to beg him to stay as usual, but I'm done. I finally feel like I can relax because the end is near, so I'm not so irritated with everything he does and doesn't do. Two days later he said he wants to be around me more now than he ever has. He says he wants to plan on getting divorced eventually, but not tell anyone, and in the meantime have an open relationship. (Which is way beyond my boundaries, but I told him that even though I'm not comfortable with it, I would think about it - really just to buy myself time and keep him from a raging melt down.) Here's the kicker - minutes after our conversation about divorce upon his return and two days before he "just thought of" trying an open relationship since we have nothing to lose, he signed up for a sugar babies/sugar daddies service. He immediately made a profile, paid for premium membership, and is now exchanging messages with one of them. Funny that his ADHD has helped me in that he forgot that his email is on our home computer as well. He has no idea that I know and I'm waiting to see a new therapist in a few weeks to figure out how to proceed.

He had a 2-3 year sexting relationship with a woman he worked with. He had an escort text him which he claimed was a "cold call" and then was furious with me for questioning him. I'm 99% sure that he had a one night stand on vacation. All these things I've pushed aside to stay married. My parents were divorced and I've never wanted to put my children through it, plus I've worried about how he would be as an ex-husband if he's this bad thorughout our marriage. I've put up with his drastic mood swings and multi-day silent treatments. I almost never get his full attention. I often feel completely unloved, and I'm shocked when mutual friends tell me how much he loves me and how great our marriage is. I'm in the best physical shape of my life, I get hit on by 20-somethings who tell me how lucky my husband is, while he has gained 40 pounds. I'm kind and loving and supportive and everyone tells him how lucky he is to have me - to which he gets jealous and says "well she's lucky to have me" He's bored with me just like he gets bored with everything else in his life. I kept trying to "not be boring" as he said - as it's always my job to make the changes to keep him happy - but I will never be enough for him. He said he wants someone who can drop everything and just have fun with him. Everything must be spontaneous or a surprise. Planning is "boring". I'm so tired of being the responsible one, the parent. I'm tired of doing literally everything, including help in his office when needed. He "makes the money" so I do everything else. Oh and I'm not even getting into the financial mess he has created...

Despite it all, I still love him. There's a good guy in there. Sadly it's everyone outside our marriage who gets to enjoy him. And even more sad, I've lost every ounce of hope I had that things could get better.