Was I wrong?

My mum's on and off again arse of a boyfriend just walked out, saying he'll never be back again.
Why?
That would be my fault.
After he tried to make a snide remark about me not saying hi when he arrived and not doing some computer thing he'd said he would pay me to do, I finally said what was on my mind. I brought up the fact that he didn't pick me up for school the morning he promised to, leaving me to walk 40 minute to college and arrive late to lessons.
The fact that it was only a week after he had walked in the house, shouted at my mum, slammed the door, came back in argued some more and left. I would later find out that this was due to the food my mum brought home from work for him, having rice on. After refusing to scrape the rice of for him she expressed the fact that she wouldn't be bringing him food again. This was cause for his storming out. Now is probably a good time to let you know that this 'man' is over 40 years old.
Finally, I can't remember how we got to it, but I alluded to the fact that he has done A LOT to my mother in general, alluding to the time I came home from my dad's to my mum. Who had a broken nose. And my 11 year old suspicions were confirmed by a babysitter, of all people, that it was him. Now you would think that when your girlfriend's teenage daughter says that too you, whilst quite obviously being close to full blown tears, that you would leave it at that, say sorry, and for lack of better words, get lost.
But no, he then had to make it clear that he couldn't believe that when he had been around I had been thinking that, because of course he is the hurt one in this situation, when I tried replying (after googling how to stop yourself crying in front of someone, rather useful btw) that wasn't allowed he had to get his hurt out. Apparently it wasn't okay for me to say "a lot" when he asked what he had done to my mother. But I really didn't want to bring up the domestic abuse I've to this day never really discussed with my mum. Whilst leaving he then some drivel such as "this is what I was talking about, you always lie. You need to tell the truth, you telling people thing when I'm not around. That's it, I'm never coming round here again blah blah blah" (imagine hard to understand Caribbean accent) . Effectively blaming my mum for everything. She shut the door when he'd gone and said
"Thanks a lot sam"
(Sam being me)
So it was my fault. And now I'm holding back the tears.
Was I wrong to have said what I was thinking.
Was I wrong to have responded "its not much of a loss" when I really wanted to shout how could you not be on my side?
Am I wrong to think someone else out there has lived through this kind of situation too?