I know how this goes. In fact, I know almost exactly how this goes. Like you, I'm 41. My parents never had a chance, and my father married a woman who liked the idea of me but hated the actual me when I was 5. Things were bad at first, and got worse when they had their own kids. I got physically abused probably once a week and mental abused almost every day. They had a shitty marriage, horrible communication issues and lots of immaturity, and both decided that their relationship problems were my fault.
I left when I was 14. I went to visit my aunt and uncle one summer and a week later called and told my dad I wasn't coming home ever. He hung up on me. My aunt and uncle saved my life as I thought of suicide frequently. Unlike you I didn't have to go it alone, at least not until my aunt and uncle divorced when I was 17.
At 41, the major result of all this is that I am fiercely independent and pretty confident at dealing with life. Aunt and uncle helped their kids through school; my dad told me to fuck off and only helped his other kids. Whatever, I'll do it myself. I borrowed money, got a STEM degree and paid my loans off in 4 years (dotcom bubble FTMFW). I owe him nothing. Yes, it's left me with some lingering anger issues that I work on still. It also left me with the ability to cut people out of my life and not look back if I feel they're not treating me right. The jury is still out on how good of a thing that is.
I'm grown now, but part of me still wishes I had stayed and dealt with my dad's rage rather then walk into that tiny little mobile home and suffocate on the pain and anguish of knowing my dad died alone.
I've thought this too. I think it comes with the age and you look back at those times with the wisdom of a middle aged person who has had decades to figure out life. But at that you you barely knew what the hell was going on. As my own kids went through their teenage years, I got a refresher in how a 14/15/16 old views the world, and how they simply don't have the tools emotionally to deal with their life and trying to manage the emotional well being of someone who is 20-30 yrs older and supposed to be their caretaker. And it just reaffirms the fact that I did the right thing by leaving. I suspect you did the right thing as well.