If things are that bad and she gets violent, police can always be involved and she can be removed from the home. No sense for violence! It mostly sounds like you, your dad and your brother need to sit down and discuss what to do. Can the three of you make it without your mom's income? Maybe downsize to save money? There are options!
Do you want to confront her for YOU? I mean, it sounds like obviously your dad does, as he's been monitoring her drinking habits and asks you the question "what will you do if things get ugly". Sounds like everyone's tired of her drinking, as your dad's statements to you and your post here. Family meeting, just the 3 of you, would be a good place to start.
Sorry you have to be here too, but welcome anyway!! The people on this site are awesome and have a TON of experience and really good ideas!!