I've decided we've got to break up, but I don't know when

In recent months I've come to the realisation that my current relationship needs to end.

After becoming depressed and volatile, he cheated on me back in November, and despite him sticking to his promise (that he'd stop drinking and quit nicotine), he's becoming increasingly more argumentative and prone to snapping on a regular basis. If we start bickering, instead of it being loving and amusing like it used to be, it always ends in his rage and me feeling like a nag. I've fallen out of love with myself and my body, and our physical relationship is pretty screwed as a result.

Today we were driving on a 70mph road and I had to suddenly swerve because there was a large box in the road. When I asked him to ring the police to let them know about the box, he refused, saying someone else had likely done it already. Queue debate, which resulted in him imploding from like a 30 to a 100 and phoning the police after screaming at me - while I'm still driving at 70mph I should add. After the call he then proceeded to make me out as the bad guy? He said I made him feel like a 'dreg' because I said he was putting lives at risk by not phoning the police, and then he had the gall to be like "and now you're crying, great". He uses this every time I get upset during a fight to make out like my crying is a way out of an argument, when in actual fact, I'm both terrified and trying to control my emotions to stay rational.

It's been getting worse the past few months and I'm at the point now where I know I can't do this for the rest of my life. However, his financial situation is incredibly tenuous and there are social aspects of our life which are so intertwined it would mean either me or him having to cut out people I've known since I was a kid and who he relies on financially.

Truth be told, I'm scared of becoming "the girl who ruined his life" and feel like I'm holding on for him to either cheat on me again or for him to fall out of love. I know this sounds like the cowards way out but I'm scared of all the alternatives.

The worst part is I'm still very much in love (so not rushing to get out) but I know I'll be sad to go. I just don't think I can handle the mental fuckery much longer.

Any advice/words of wisdom/comfort appreciated.