I'm so sorry things have come to this unhappy place, Lava. However, I think it's better for all that they are out of your home. I'm glad you got to say goodbye to little GS and have a "cuddle" though.
IMO, this was a matter of mismatched expectations, miscommunication (between the young couple, as well as between you and them), and, of course, outright lies, as much on DS part as DIL's.
I agree that some culture shock may have been involved, too, even if just "family culture shock.' It seems both DS and DIL expected you to be like her mom and failed to respect the fact that you're an individual in your own right, w/ your own needs, beliefs, etc.
Perhaps DIL's MH is also a factor? She/they may have thought you would understand that. But none of this excuses her rude behavior.
I'm sorry DS isn't communicating w/ you right now, but he probably doesn't know what to say or wants to work things out w/ DIL before he answers. Better, IMO, than when he lies or confuses people. Glad you've stopped messaging him. Please be patient and wait till he reaches out to you.