This is the 3rd time in a week I've heard about a dope-smoking partner and the problems they cause.
I am going to repeat: dope-smokers are not chilled out people. They are a total nightmare when they haven't got any weed, will go to any lengths to get it (taking children with them to the dealer when any sane person knows that is totally out of order) and often become small time dealers themselves, selling to friends to make a bit more cash to buy more weed.
The house stinks, their clothes stink, the cupboard where they keep it stinks, they skin up on the side in the kitchen and leave bits of skunk around that one day your kids might try.
They try and convince all and sundry that they are a chilled out person, that all pot smokers are, and that if you are not then you are a nag/stress head. They are only chilled when they are rolling/smoking a joint. The rest of the time they are either asleep or getting shitty because they want a joint.
All your time and resources will be used up looking after him and his habit. As you already know, your children come second and you come third. Why oh why oh why put him and his drug use above and beyond the children and yourself? Him and his dope smoking cronies might want to convince the world that they are chilled out deep people, but actually they are just addicts and whilst he's on it you and your children pay the financial and emotional price of living with him.
I'm being straight up with you because you need to hear the reality, rather than the dross your partner probably comes up with to excuse it. I totally understand being sucked into that world - been there done it. I wish someone had confirmed what I was thinking a the time, instead of listening to all the fuckwits without children telling me to 'chill out'. They weren't there when he kicked off.