I'm sober now :) and have started to process what happened.
We went to a pub for lunch. Dad started apologising for missing 20 years of my life, and said although he can't make up for it, he'd like to make things better between us from now on.
He acknowledged the pain he'd caused me by some of his decisions, and apologised. I was honest with him, and told him I'd thought of going no-contact recently. He listened. I wasn't on my usual 'best behaviour' mode, and spoke openly about what he did and its' impact on me and DSis, and how shit my childhood was. [He says he didn't know about the dv I witnessed.] He expressed regret for cheating on my ex-SM - DM had previously cheated on him. And for not looking after me and DSis like he should have. He acknowledged that he'd concentrated on his wives and sidelined us.
In hindsight, it struck me that he's had some kind of personal realisation. I don't know why, whether he's had counselling or whatever, but it was good to hear him being honest for once. He sounded like he realised that he's fallen seriously short, and wants to be a better man.
At points he had tears in his eyes. He didn't cry at his mum's funeral. The only time I have ever seen him with wet eyes was at my second (happy, unlike the first) wedding.
I cried last night for how our relationship could have been. I'm experiencing a weird mix of emotions. Happiness because the dad I met yesterday was a more honest, open and loving man than I've ever seen him. Sadness for what has gone before. Frustration that he didn't realise this years ago. And hope for the future, but fear that it's just a flash in the pan.
We'll see :) Apologies for mega-post!