@Elfingbell This is a really heart-breaking thread to read. Your opening post was bad enough, and with that, you immediately had my sympathies, but this thread had descended into so much more. Thank you for being so open, I'm not sure I could have admitted some of things you have posted about on here, particularly your behaviour towards your SM and S.
I've read each of your posts and can't say I agree with the people accusing of you of only caring now that you have 'lost everything'. Going through the trauma of what you've been through in recent months would have no doubt made you reflect on the past and seen things with a clearer perspective. In some ways, watching this thread develop and analysing that way in which you've opened up, it's clear that the flat in London and exdp are secondary issues (which I don't think is a bad thing) and that the anxiety you've had about your relationship with your DF and SM has always been there. London was just escapism; a temporary fix and a way for you to supress what had been bubbling away at you. This was always going to come back to roost, and fixing things with your family was the only thing that would have set you free - not the fancy flat and great job.
I was quite taken aback by your DF's response to you, I wasn't expecting that at all. At the same time I thought fair fucks to him for calling you out for being an absolute arsehole and getting away with it for years. but what was telling from his text is that those two incidents that he referred to have clearly weighed on his mind for years, and have affected him personally. You'll have to live with the pain that you caused him, and he'll have to live with knowing that he defended you for doing awful things, to the detriment of SM and S.
Your family is great. I come from a dysfunctional family and reading your posts about dsis and your step siblings made me almost feel envious. And that email from step-sis was just wow! She really is incredible and your dd will be SO lucky to have aunts and an uncle like that.
I'm rooting for you OP. Please keep us updated. I'm so excited for you to mend things with your SM - she really does sound like a wonderful person, who also raised some great kids - your DF has good taste. Wishing you and DD the best of luck!