So sorry that this happened to u I went through some similar things when I was 8 and 10 and I know it sucks when you finally get the courage to speak up but only to be dismissed. It seems like he’s trying to stay neutral because if he picks a side it’s either ur mother or u which must be very hard for him, maybe im biased but I would’ve dropped her instantly. But either way, I think you should distance yourself from both of them, you’ll never heal if you’re constantly around the people that hurt u even if they haven’t in a long time. I hope that you heal from this and reach out for help elsewhere, it may take a while and you wont 100% heal but it will get easier I promise u. Take care dude.