My condolences on the loss of your mother. I could not imagine that pain. My heart goes out to you

And yes in laws can be the absolute worst. Some like mine, are super toxic.. Constantly trying to tell you what's what and whose who. After years of MIL shoving herself down our throats I've learned that the best option is distance

I have their son do most the visiting and I just stay back. I see them when I must but definitely not often. With certain types of people, when you stay in close contact with them its like they cannot refrain from digging into your business. They pretend it's their job when its simply not. Their children are grown and they should accept it

Basically my advice to you is to have a long distance relationship with them, never giving too much of your information out. Good luck to you and my sympathies for dealing with bullies