OMG OP - you’re seriously onto a hiding too nothing with this man! You’re worth so, so much more. From what you’ve written he reminds me of my ex husband - a duplicitous, spineless weasel of a man, who lies convincingly as easily as drawing breath.
From your last post it sounds like he’s basically told you that he’s only with you because of the DC, and he can’t ignore his strong feelings for the other woman, but he can’t erase you and the DC either?! So, if he had the courage of his convictions he’d be with her? Absolutely fuck that for a game of soldiers.
it shouldn’t all be about him and his feelings/wants/needs. It should be about you. He’s repeatedly pissed all over your marriage, yet you’re still tying yourself up in knots trying to work out what his real feelings/intentions are. He’s a screwed up, damaged person. Only damaged people go on to damage/hurt/use other people the way he has you. But you can’t fix him - it’s not your job, and possibly not even possible. This isn’t your fault and he isn’t your responsibility.
What is your responsibility is to do what’s right for you. Of course, nobody can tell you what ‘right’ looks like for you personally. But for the love of the gods, don’t stay with a cheating, lying dickhead for the sake of the DC. It’ll do them no favours to grow up in an unhappy, distrustful household.
I found out about my ex’s affairs when several mistresses started sending cards and gifts to our house during lock down. When I found out about one affair it was literally game over after 16 years - there’s no way I could be in a relationship with no trust and I could never get past the disrespect and deceit. When I discovered the other affair a couple of weeks later it almost didn’t matter - the damage was already done and I’d already helped him find a flat and physically helped him move out (as I couldn’t get rid of him quickly enough).
Almost two years on at this end, ex is in a boyfriend/girlfriend relationship with one of his mistresses - she lives in London and we’re quite far away, so they don’t live together full time. I haven’t met her but she’s hugely kind to my teen DC - she moved to a larger but less fancy flat so DC has a bedroom when they visit for the weekend. I have no animosity towards her, I just feel a bit sorry that she doesn’t realise she can do much better than ex!
I have a wonderful fiancé who loves me like I’ve never been loved before and the feeling is mutual. I didn’t expect to find ‘the love of my life’ in my mid 40’s, but life is funny like that. Ex and I are amicable but I’ll never believe a word he tells me again. He’s not trustworthy - literally not worthy of my trust.
Anyhow, my point is that there is life after marriage to a cheater. It’s not easy - splitting up, divorce, practicalities with DC can be tricky at first. But to my mind it’s a million times easier than staying and flogging a dead horse. If the marriage is a shambling zombie of a marriage, the kindest thing is to take a metaphorical baseball bat and smash the brains out of it - put it out of it’s misery and bring it to an end. It’ll be less painful in the long run.
Obviously this is only my opinion and my experience. I’m sure there are lots of people who’ve worked and worked on it, cried their hearts out, flogged their guts out to try and make it work - and I suppose sometimes it does work and it’s worth it for them. But to be honest, someone who treats me so poorly and disrespects the family we built isn’t worth that much of my time, head space and emotional effort.