I appreciate how difficult it would be to have a brother with schizophrenia who is hard to communicate with, paranoid, abusive, and irritating to talk to. I don’t think there’s any merit in forced communication — just because your parents think it’s good. It doesn’t sound like it makes him feel better, and certainly doesn’t make you feel better. Your parents can hardly see it as a success.
I suggest three things: first and foremost to take care of your self. Don’t be doing these talks out of some kind of weekly obligation. Doing it out of guilt or responsibility isn’t healthy — for anyone. Instead I would encourage you not take part in the group FaceTime and shift to more individualized contact. Be direct. Let your parents know you’d like to talk to them separately from your brother so that you could call and catch up, this might also include talking one-on-one with them, but importantly this is these are conversations without your brother.
Secondly let your brother know that you’d want to talk with him individually from time to time. Put the responsibility on him for calling you once a month and you could call him once a month. Make sure you keep up your end of the bargain regardless if he does, and he can decide if he wants to keep up his. Just be sure you don’t let him abuse you when you are on the phone. Hang up by saying you are uncomfortable with how you are being treated. This isn’t a debate. It is the last thing you say before you hang up. Letting him berate you serves no purpose.
Finally I recommend doing a loving kindness meditation for your parents and your brother. Generating these compassionate feelings as you are lessening your contact with him should help emotionally with the process. You aren’t doing this to be mean — you are doing this to take care of yourself.