No, it's not Lobster Boy. That was my thread and a long time ago, but I am amazed and humbled some of you still remember it.
It isn't going well to be honest. DD is becoming more and more distant. She and her sister are no longer on speaking terms after LB kicked off at the time of her sister's graduation. DD still has some family love, I think, and came home for a couple of days before Christmas, but seemed like a stranger. She says we never welcomed her 'life partner' into the family and he 'speaks truth', she sees us all differently. LB says he doesn't want anything to do with any of DD's family, even though I was the only one who fell out with him. I am not entirely out of contact, but there is resentment, she has stopped replying to messages, and I don't want to bombard her or put her under pressure. Ultimately, the fear is that she may cut contact with us, as a means of coping.
When she came to stay, she said - off guard - she had made all his meals for two days and written down when he had to eat and what he had to eat - or he would just eat biscuits.
My DH spoke to her a few days ago, said - which she agreed - we must keep in touch. She said at Christmas that she loved me, but I feel it's all hanging by a thread. I feel in despair to be honest, and torment myself by looking at threads about estranged DC and thinking this may happen, what have I done wrong, what could I have done differently.
On the plus side, my other DD are as loving and close as could be, so I must cherish that and live in the present.
But OP, so many parallels, DD's other half, when we saw him, was lacking in politeness in so many ways, far more than your potential son in law, to the extent where I also wondered if he were on the spectrum. Neither he nor DD have worked since graduating two years ago (apart from DD had a holiday job in 2015 for 3 weeks). Neither of them want to get jobs, as they are 'different from other people' and don't want to be 'wage slaves' or 'mortgage monkeys'. She seems happy, but I wonder where the future is. If the relationship ends, she will have nothing - no home, no job, no money. Of course we will be there for her and I love her so much that maybe she has to let us go to be happy and I don't want her relationship to end if she will be unhappy.
But it is so hard. I worry constantly, I don't sleep. Sorry, I don't want to be a 'pity party'. Just be careful OP, be very careful.
I worry so much about her, but anything I say is rejected. I am sure that he reads all of her e-mails and discusses how she should respond to everybody, including her family. They are together 24/7.
There is so much more and I don't want to hijack OP's thread. I am desperately trying to hold it together. I should have kept my mouth shut. I wish I could go back in time; whatever money I lost would be worth it not to lose her. I don't know how it will end. He is controlling and dreadful, but he controls her. As the saying goes 'Keep your friends close and your enemies closer'. He was and is my enemy, but I lost my sxxt and didn't keep it together, as I should have done.
OP, my firm advice is to put up with him, however bad he seems. Hopefully, your DD will see the light, but she may not.