Hi Whitetulips
I am in exaclty the same position - my H and I seperated in the NY, after I found out that he was seeing somebody else (He denied and denied it but still moved out !).
I then found out about 4 weeks ago, after him totally denying it, that he had been introduced to OW's family (Mum, Dad, Aunt etc), so I was furious, but we were still staying friendly, and OK for the sake of our DS.
I didn't even fly off the handle when I found out that he lied to me for the last year or so (Which also coincided with my Mum having a dreadful accident, falling down the stairs and being paralysed, and then passing away in March this year). I still kept it together although he was totally unsupportive. We agreed to start divorce proceedings (I haven't put it down to adultery, as I didn't want to annoy him, and just wanted the whole thing over with).
We went to relate last week, and I asked him for what I thought was a fair financial settlement (Didn't want to touch his pensions/endownments/redundancy money etc), and he went mental, and has now decided to start trying to take all of my friends away from me (He wants to take OW to a dinner where all of my friends will be) and he is very manipulate and clever.
We have gone from being OK with each other (Having a coffee and discussing our DS) to him hating me with a passion, all because I have asked him for money to help me support myself and our DS.
He has recently lost his job, but will get another one, normally is very very well paid, but is totally obsessed with money.
I sit here and wonder if we will ever get to the point where he will be reasonable with me, and allow me to grieve for my Mum and not spend my whole time fighting him.
Sorry for the rant, but I do know what you're going through, and it makes life so very very hard, and especially when it was none of our making.