Healthy limits,
Posting, getting your thoughts out of your head and onto paper, or a computer screen, helps. That is why we are all here.
Both my mom and dad were alcoholics, and my mom's drinking started because it helped her endure my dad's violent outbursts and absence from his four children. And she silently endured all the excuses and abuse and never made a move to leave. I believe she felt she was doing it for the kids, but there is little question that a divorce/separation would have been far better that watching her destroy herself.
I am only throwing my experience out to emphasize:
1) you cannot control other's behavior, only your own.
2) keep the lines of communication open unless it is actually harming you, preventing you from working through your guilt.
Thanks for posting. I have not heard a story so similar to that of my parents. Both have passed away, but the fearand guilt and anger lingers. I hope and pray that the situation with your parents get resolved while you still have years left to enjoy.