Those are all normal feelings my friend..all of them! You are not to blame for his choice...but only time will make you understand that. It's called acceptance and you are a long way from that.
Psychiatrists would tell us that as human beings it's our nature to resist the idea that we cannot control all the events in our lives and we would rather fault ourselves for a tragic occurrence than accept our inability to prevent it.
And it's usually a solo trip..we each tend to blame
primarily ourselves.
I remember so well feeling as you now do....you are only a year or so out from his death..it took me
years to accept it and a lot of hard work.
Please keep talking about your brother and try to be kinder to yourself.