@notrose6 I am sorry for responding so late - your post deserved more than a few rushed lines while I was at work.
I will say to you what I say to everyone on these threads who has lost loved ones: everything you feel is valid. We tend to beat ourselves up with how we 'should' feel, but life with an addict does not conform to 'should' and neither do we have to.
You protected your young child from witnessing your brother's self destruction. Please know that this was 100% the right thing to do. You walked away because you could not help - that too was the right thing to do. Protecting yourself from the influence of an addict on your life is not selfish, it is sensible.
What happened to your brother is not atypical of someone addicted to alcohol. The human liver is a wondrous organ: it can take decades of punishment without showing any signs, without so much as an abnormality on a blood test. But when it does go, it goes with a bang from (on the face of it) fine to terminal. It isn't even about how much your brother was drinking; it's just that his liver reached its breaking point.
Your family's reaction to your brother's situation is theirs to own, not yours. You are allowed to grieve in whatever way seems right and natural to you. And please don't feel guilty about 'detaching with love' - it's an Al-Anon trope, and Al-Anon are notorious for always trying to keep families together, whether that is siblings, parents/children or spouses. The detachment they promote is emotional, not physical and you are expected to stay in the situation. This is very unhelpful in very many cases. I didn't detach with love either. When the police took my husband away, my first feeling was relief. When the police called 8 months later to tell me he was dead, my first feeling was relief. And that was a legitimate way to feel.
It is quite likely that you will end up having to deal with complex bereavement; if you feel that it is affecting your quality of life to the point where things are unsustainable, please do seek professional help. It was a sanity saver for me and my DC.