Hi, Stewy. I agree with Leviathan--you sound like you are on the ball and that sobriety has brought along some clarity about the relationship.
Just to share my experience, I had a similar situation with a partner many years ago (he wanted to go to graduate school, and wanted me to support him, financially and otherwise). The problem was that at this point our relationship was pretty frayed, and I knew in my inner heart that the relationship wasn't right. Listen to that voice. And see that reaction (screaming) for what it is--a huge red flag. In respectful relationships, a calm discussion should be able to ensue when we share that something isn't going to work for us. But boundary pushers just react in the way that your gf (and mom?) reacted. One thing I try to remind myself is that sometimes someone else's displeasure at my decisions is a sign I'm doing the right thing for me--that is, that we cannot always please everyone around us and be true to our desires and needs.