I feel for you, OP, I really do.
I have been through very similar to what you so sadly describe.
As a once wife, who's husband (and I use that word loosely) had affairs just because he could (he was in the RN at the time) to being in the same situation as you are now, with my now husband.
We have been together for nearly 25 years, married for 21, but his daughter, who is now 28, has had no contact with her dad since she was 17. She is the same age as my own daughter.
Her mother had an affair, left her dad for the affair, got pregnant with him and married all within 18 months.
We got together just before she found out she was pregnant, BUT, lo and behold, I suddenly became the OW! Blamed for everything, even though I was a stranger to her. His daughter, obviously, was told I was to blame for everything, and consequently there was no recovery.
On the other hand, my ex has now been married another 4 times, our children went to 2 of those weddings. I left them to make their own minds up....and they did. Now they are both adults, married with children, they have no contact with him at all.
So both my 'husbands' are losers with their children, one because of a circumstance that he had no control over, and the other because he just didn't give a shit.
But my husband today, is a winner - grandad to my daughter's beautiful children and he adores his step-daughter, as she does him.
His daughter is also now a mother herself, and he lives in hope that one day she will contact him - he has NEVER changed his mobile phone number for that reason.
I wish you the very best in sorting out your situation, I really do.