Some pot users claim that there is no marijuana addiction. There’s absolutely and widely recognized cannabis addiction. Not just dependency (which is pretty much the same thing) . Also it’s not true that marijuana just mellows people down. Cannabis psychosis is also well known reaction to pot. So every pot smoker could become potentially dangerous at any point.

He’s not going to stop because of your begging. You didn’t cause it and you cannot cure it.

No it’s not pathetic to leave someone due to substance abuse. You have rights to live your life the way you see fit. Your children have rights for healthy life style. Addiction and substance abuse is a very serious and valid reason to leave a relationship. It’s not like you are leaving him because he leaves a dirty coffee cup on the counter. This is serious