What strikes me as interesting about this thread is that, whilst the positions are very polarised and that has, clearly created tensions, there is some useful advice that the OP can use to take the situation forward.
The interesting thing, to me, is that most of the actual advice has been from the adult children who grew up in similarly abusive households. The advice has also been fairly consistent. Why? Because we understand what either helped us to move on from it or, by the same token, prevented us from moving on from it and families becoming estranged permanently.
The people who are 'supportive' of the OP are either echoing the same advice with the caveat of "as said by previous posters" (e.g. the adult children I mentioned above) or empty, useless meaningless platitudes: "I hope your son comes round"; "I hope things work out for you"; "You're so brave". All perfectly acceptable and well meaning sentiments but utterly, utterly useless to the OP in resolving the situation she finds herself in,
Or, worse than that, bad advice e.g. "write to him and tell him how you feel"; "explain to him why you made the choices you made" which will, literally, be like pouring petrol onto a barbeque.
I'm sure that you all feel very proud of yourselves for defending the OP and being 'nice' but has any of it been 'helpful'? I doubt it.
Oh and as for the accusation of people being MRA trolls, I'm well aware that you are being a gf and just trying to get a rise out of people but, on the off chance you actually believe this, do you really think MRA activists have a great insight into and empathy for child victims of abuse? Grow up.