When you’re called a liar so much you start to believe it - what should I do?

So this might be a little long but I need to give background info to understand

I’ve been with my now fiancé since the age of 13- now I’m 21. We have a 16 month old daughter.

My fil is an extremely sexually inappropriate, touchy feely man. When I was an underage girl, he was inappropriate with me several times (touching my booty, fondling me etc) making sexual comments to me infront of my mil etc

I’ve now in the last year or two come to terms with how inappropriate he was with me and have since decided I want nothing to do with that family except my fiancé- and I definitely don’t want my daughter around that.

We always really restricted my mil and fil access to my daughter, but they never knew the reasons why.

So back in august 2019, my fiance finally sat down mil and explained everything to her. She even said she knows what FIL is like.

It never went anywhere from this fil was completely oblivious up to last night.

We literally JUST booked our wedding last night and we were so happy, then literally 5 mins later mil calls me (she never does this) and abruptly asks to speak to fiancé. He goes in the other room and next thing I hear him screaming down the phone- he literally never gets angry.

Apparently my mil finally had the balls to say that she doesn’t get to see her granddaughter because I think he’s a sexual predator and he has touched me inappropriately before.

He was crying and swearing blind that it’s not true and I’m a liar and I’m brainwashing fiancé. I had his sister being abusive saying the same things.

They threatened to come to my home to “sort this out” when I’m literally terrified of them, I don’t want them in my home intimidating me in front of my own child

Now mil is sticking by her dirty husband and believes im a liar.

My fiancé works for them as family business and he saw his dad face to face for the first time today. His dad threatened that “he won’t be around much longer” which of course me and him would be blamed for

I don’t think I can get through this