Your post really speaks to the fact that addiction is a family disease...
I am the mom of an addict and I too became so consumed by his disease it was all i could think or talk about....my other children must have felt just as you do now.....
it took a long time and much recovery work (on my part) before i was able to "let go" emotionally from my AS and begin to enjoy and appreciate my sober children....at first, i just forced myself not to mention AS name....if they asked about him, I'd answer briefly and then changed the topic back to them....(its exhausting just to recall those days....)
I know how hard this is for you....you are right to stay off the rollercoaster...
I was so happy that my children managed to do that...it was bad enough that i was going under (at that time) with their brother but no mom wants to see everyone going down!
I pray your mom will find peace of mind...a way to recovery for herself....
may your brother reach out for help and start his journey back...
take care of yourself!