Welcome trickytiger. We're glad you are here!
I can identify with the relationship you had growing up and now have with your brother. My relationship with my brother was and is much the same.
We've all been through relationships similar to what you described with your boyfriend. I made the huge mistake of marrying mine. I loved and still do love him but I had to save myself and divorced him in Jan. after six years of marriage. Be thankful that you had the insight to realize what was going on. I guess I was partially in denial and also not educated on alcoholism. I had never been around it and didn't have a clue as to the insanity that would become my life. Now I'm working on me and life is much, much, better.
The fact that you know you need help to work through it is commendable. This board saved my life and AlAnon is now a source of constant support.
It sounds like you have a bright future ahead of you. The time you are investing in your education will pay off for decades. Spending time now working on YOUR recovery and learning to make better choices will have an even bigger payoff. We're all works in progress on here.
Hugs to you.