I rather think that both these threads have got alot to do with feelings or lack of them
The more I read, the more I realise, it's all about the love.
OP seems very logical, to the point where if her marriage broke down, well ho hum, she would assume it had been an unhappy marriage and shed no tears. OP is independent of her DH, to the point where she supports herself, and doesn't believe her DH should take much of a fatherly role where her DD is concerned. OP is extremely logical, almost unrealistically so.
Her DH and XP seem to both be displaying feelings. DH seems to feel guilt towards his shoddy treatment of his X, and assuages this with maintenance and providing a roof over XP's head, and the heads of her DC.
XP is clearly hurt, and angry, and whilst I absolutely do not condone her abusing OP at all, I am getting a picture in my head of a very frightened angry woman, who is scared she is going to have the rug pulled from under her. (XP, not OP)
DH seems to sense this and continues to provide for XP and DC.
OP seems unable to truly appreciate how other people feel, and what drives them to behave how they do or do the things they do.
I have a sneaky suspicion that OP in fact feels rather threatened by the XP, doesn't understand why her DH continues to support his XP and her DC when he has no obligation to, may have crossed her mind more than once that her DH will leave her for his XP, and after seeing how fast DH has been able to move on before (matter of weeks) is exercising self preservation in being so logical, since she is worried it may happen to her, and she doesn't want to be hurt. She probably doesn't show her feelings to people easily, but what I find most astonishing of all, is why oh why is the XP still being so abusive 2 years later??? Something is not right!!!