My Ex is driving me mad HELP?

We went out for 9 years through our teenage years into our 20's, We parted mid 20's and met again 12 years later, we had a quick fling and then fizzled back to just being friends. It's weird, I know I probably deserve a slap on the hand for having him back in my life but we talk/text as though we are a couple and yet we are not a couple. He often takes things I say the wrong way and looses his rag over nothing. SO this evening, he misinterpreted me joking and he basically turned into a male version of a *********. He slammed the phone down shouting "I'll ring you tomorrow right" and wouldn't listen to me explaining what I had said that he had taken the wrong way. It put me a bad mood all evening, why am i even bothered by this? Why are we maintaining this connection often supporting each other when he has a live in girlfriend they just bought a house together and i dont really want his temper tantrums back in my life! It is crazy I know but it's almost like we feel we should hang on to each other after being friends since 1985...like we know each other inside out but God he still vexes me so bad - part of the reason we broke up all those years ago. I'm confused I dont want to argue with him I'm not into conflict and rows and being angry - he is and always has been quick to fly off the handle at anything he doesn't get. OOOooeeeeerrrrrgggh what do i do?