Do I snitch?

So before I tell this story I think it’s fair to mention I might be bitter towards my dad for choosing his new “family” over me and my siblings and him always being out is hard on my grandma too since we don’t have a mom around.

With all my bias laid bare, here’s my situation:

My dad got divorced like a bit over a year ago I think and he’s found a new girlfriend. He was a piece of crap in his second (most recent) marriage, and I was too young to remember his first. He argued with her every night cause he’d drink every night. One night, he said smth around the lines of “Get the F*ck out of my house or I’ll sh**t you!”. He was drunk and ion think he held a g*n to her or nothin but that’s literally THREATENING her. (He never actually hit her or anything actually physical tho unless I js never heard that story).

Idk if he’ll be like that w this new girl and I feel guilty if I don’t warn her and he does treat her bad. She has two young kids and I don’t want them exposed to this bs they don’t need to hear it and ion wanna risk that for them. But I don’t know how he is with her she lives an hour away so I don’t see her much and he’s always there.

If I did tell then first of all I’d be so screwed I can’t drive yet or legally move out or nothing so I’d screw myself over big times snitching. And those kids don’t have a dad, he died last year in a bike accident. I don’t wanna take away their “new dad” over nothing but I don’t wanna let them hear all I did. Idk what my dad would do if I told too (he’s never threatened or hurt me- only ever yelled or grounded me but still what if yk?).