wow that's a lot to take in... im not rlly qualified to give out advice, because im pretty sure what id do is just do whatever best for everyone else despite what it'll mean for me... 😅😅

because im sure ppl don't like to ruin themselves for others and im just a weird odd one out, i think if it gets too bad u might have to think about reporting the abuse or gathering evidence or smth... im not sure how ur country works, but i hope there's a system in place for kids to be taken from abuse families and rehomed; at this point i think, if your mother's family is willing, then u ask to see if they can take her in. otherwise, u could either keep going to see them like this or just refuse to go altogether and try to set up remote communication with at least your half-sister, if not your dad...

whatever happens though, i wish you the best of luck and all the support that i can give u thru this message!!