I’m not sure telling a 10yo about an affair (you even said ‘we suspected’, so you seem to have been heavily involved) is the healthiest thing. Maybe your mum was very alone, but a 10yo daughter isn’t really supposed to be your confident for adult matters. Mine did the same, except started much younger, I don’t really resent her for it, I don’t really see the point, she was alone and desperate and coped in an inappropriate way, but that’s life.
I think you were way too young to process, and even decide at 11yo not to see your father is a bit young ime. Did your mum encourage you at all to keep seeing him ?
Basically you had ime way too much information and ability to choose in full capacity.
Re: affairs, yes he didn’t go about the whole meeting someone new well at all. It’s not hard to end the first relationship properly, explain in simple words he met someone else, and then move on. Fwiw though, I was a bit older (14) when my mum had an affair, and she shared all the details, and she actually really did love him. Affairs are obviously the wrong way to go about ending relationships, but I don’t really see anything wrong with falling out of love and falling in love with someone new, after min a decade people can evolve differently.
And your dad honored his child support engagements and still gives you money at 25.
Sorry if this was long and written a bit quickly, the conclusion is that none of my parents discouraged contact at any point, despite my father completely non contributing financially (at least you had a house to sell, we ended up for years with my mum and brother in a tiny studio). I’ve accepted at 32 that people make mistakes, life can be messy, and I’m in contact with both parents. My dad also remarried and I’m glad he’s happy.
I think my vision of things is a lot skewed by health issues resulting in much too young departures in my family, including myself, I almost died in a coma from extremely unlikely complications of an organ infection this year.
Life is too short for anything other than health, and trying my best to provide a roof (however small, buying, renting, whatever), food, and education for my family. I thought so many other things were important, but they’re just a welcome bonus if so.