I understand your fear of losing control much better now. Does it help at all to know that you really can protect yourself - you dealt with the two cops! You weren't to know what the strength of your reaction would be, but I feel for you having to deal with the aftermath. I guess that's why your therapist is being careful about the approach to help you release your anger.
Presumably the abuse is far more real at the moment than it has been since it happened, with disclosing to your family, and working through it in therapy? If this is true it makes sense to me that the suicide thoughts are strong now. And there is the thing about self-destructive thoughts being anger turned inwards.
It's good that one brother apologised. Can you do anything about the other one - he sounds despicable. Can you / would you want to get a court order against him to stop him coming over? Or sue him for the abuse at some point?