vikkiO, I'm so sorry you are going through this, I would feel absolutely physically and emotionally sick about it all too. This makes me really mad at your BF for contributing to the drama and your stress. Knowing that you are very upset by his family's treatment of you and leaving without communicating his intentions to you is disrespectful and mean-spirited (and suggests they all enjoy the drama). Maybe the apples didn't fall far from the tree. I still think his daughters are being coached and encouraged to behave so badly by his EX and family (and him?). Their words and the family responses sound pre-arranged.

There is not much to do about it. You can wait until he returns and see what he has to say for himself or you can bail out and tell the whole lot of them to kiss your grits. Neither option is pleasant. The things for you to remember here:

That you entered into a relationship with him, not his family.
That you did so because he presented himself as a mature single man looking for single adult female companionship.
That your job is to be the best GF to him that you can be. It is not your job to cope with his family, especially when they have been so hostile.
That he did not warn you that he would allow his family to treat you so badly. Because this is really all about what he is allowing.
That you do not deserve to be treated like this by his family.
That he is responsible for making his family understand that it is unacceptable to be treated like they have treated you. And hold them accountable for their behavior.
That no adult would want to willingly be exposed to people who act the way his family acts.
If BF/they try to gaslight you or marginalize your feelings, or if he insists you continue to expose yourself to his family so they can abuse you, then you really should consider leaving.
If they make demands on how you should behave towards them, yet feel free to step on you, then you need to start looking for the exit.
When being around some people makes you feel crazy, stressed out, and out of control, it's probably not you that's crazy, you probably landed in a nest of narcissists and they are playing head games with you. Don't wait until they have beaten you down so far that you can't think straight.

Those kind of people rarely change, they just get sneakier and dirtier about it. I don't think he can stop them, if that's what he really wants to do. Some people are addicted to the drama. The only thing he could do is to detach from them and I bet he doesn't want to do that. I don't know if you have read up on RA or PAS or narcissists, but it may help you recognize what is happening.

Consider this a test of his emotional maturity and his commitment to you. Real men don't allow their women to be treated so badly by anybody. He could fix this relatively easily if he'd stand up to them and let them know he's the one in charge and calling the shots, not any of them. If they are so dysfunctional as to cut contact, then so be it. They are old enough to choose and be held accountable for their behavior and decisions. You need to step out of the drama from BF and his family. ((HUGS))

If you decide to leave, buy him a cat before you go (a male one, neutered of course-no balls allowed in that household). Tell him since his family runs his life and doesn't want him to ever have a life or woman of his own, he can be the lonely old batchelor with the ball-less cat. The male version of the cat lady.

And you will hopefully have had your belly full of this weird family and gone on to find a man who will put you first and be living a happy life-without them. That's the best revenge you know, to go on and have a happy life without the dysfunctional people who always tried to hurt you.