I'd just add if you cannot find an authoritative figure to help mediate; can you make yourself a safety plan? Something you can do to help cope during the surprise visits to help you feel safer? I'm not very much help right now - lot of stress in our world, but I want you to know you are cared about.
My son talks about his emotions (all..not just anger or sadness...everything) being like a reservoir with a jello dam - anything might make it all come crashing down. He's worried he cannot take out a cup out at a time to deal with in little doses or give to those who caused it....but what our T has suggested then, because that is just too much right now.... so what she has told him to do is work with just the daily stuff.
Just recording what is upsetting him and what went right for the day... she says when he is feeling overwhelmed, he might visualize doing something with the anxiety/anger/whatever - like one person uses a wishing well...she tells herself she will put the thing away like a quarter. not to lose forever, but for the well to 'hold it' for her until she is ready to pick it back up and look at it...
What we do looks like this:
I felt really (whatever) when (someone/something) (did what they did).
When I feel (this feeling) my biggest fear is . . .
What I need to happen is:
What I need from (the person) is:
Sometimes the person can be spoken to and your need expressed and even, hopefully, met. Sometimes you can either not talk to them or they won't respond the way you'd like...and at least giving yourself the validation of what you need and that it is OK to need it...helps.
Also, if you can take it one more step. Don't just leave it with "I fear this...." you must also ask if it is logical that the thing you would fear would occur or is happening...
I'm going to give an example from our own life.
I felt really angry when my brother said he would do dishes for me and didn't.
It made me feel betrayed. Also, I feared dad would blame me for them not being done.
I needed my brother to keep his promise.
(to brother: I need you to keep your promise, or let me know if there is a reason you can't. If you do this, I will have the chance to be understanding. If you don't, i won't be able to trust you...)
to self: Dad might have blamed me if he didn't know what happened...but he usually listens. When I find out something isn't going the way I expected, I could find him and talk to him. I don't have to wait for him to 'find' the dishes and get upset before I talk to him....
This is giving him control - to understand his feelings, validate them, help him communicate to his brother and to his dad....
I know this is long..maybe even disjointed...but hang in there. Hopefully i can give more coherent advice soon.