Personally I think a 39 yr old man getting involved with a 19 yr old woman was predatory.
Inappropriate and predatory.
The fact that he was cheating (and repeatedly at that) on his spouse & mother of his children is just another element demonstrating his lack of morality & integrity, and his departure from appropriate/acceptable behaviour.
I watch a lot of true crime videos and one thing I've noticed about the perpetrators of serious crimes is that they are almost always cheaters and they are often sexually involved with inappropriate partners (due to relative youth, close family member or family friend, friend's partner etc.).
(Incidentally they are also often involved in financial mis-dealings and cannot manage money responsibly).
I'm obviously not saying that all cheaters become serious criminals, but it's interesting that so many serious criminals are also cheaters and also tend to seek & take opportunities with partners who could be regarded as inappropriate (often with some element of predation).
It's part of a picture of sociopathic personality traits.
It's very likely they have a personality disorder.
I'd speculate that the married man sits firmly on that spectrum somewhere.
Personally I don't blame you, in your youth and with your background, for getting involved.
And you clearly developed some attachment - which is easy when you're intimate with someone (oxytocin), easy when someone is portraying you as a soul mate, easy when it's illicit and exciting and seems "adult".
Easy when someone is hitting you with all the lines that attached cheaters use to get and keep their other women ("relationship broken down, only staying for kids, she's indifferent to me, she's got someone else too, I can't talk to her the way I talk to you"). They use those lines/that narrative because they work. Especially on inexperienced women.
The attachment/dopamine hit etc. is probably why you were tempted when drinking, to respond.
But luckily you were able not to. And luckily it seems like your unhappiness with the situation and unhappiness with his (very ironic) jealousy and attempts at control won out.
He is not a good partner. Not to anyone. You said you've met some decent blokes. Keep looking, keep trying to meet them and date as much as you can. The 20s is when many people get involved with & build relationships with their future spouse/long term partner. The dating pool is not getting bigger after this, it's getting smaller. Put effort in and strike now.
You have the chance to find someone decent - this guy is not.
He's a washed up, middle aged, already has kids he has to pay for, serial cheater, liar and - as I said - he was/is a predator.
He does not have the rules and boundaries of a decent person, he's a sociopath to some extent.
Feel sorry for his wife - that she got stuck with someone like him as her main life partner. Don't get stuck with an even worse deal than her (because you know what he's like, and because you're 20 fkg years younger).
He is her main life partner. Even if she escape the relationship abd has another significant relationship; he will always have been a life partner and will always be the father of her children.
Meanwhile he can, as he deserves to be ,a mere blip in your life. You, unlike her, can find a decent life partner.
Look out for yourself.
Looking out for yourself excludes ever getting involved with that specimen, again.