I am not particularly judgmental about the odd spliff, perhaps if you have older children and they are off out for a night or everyone in bed.
That's not what's going on here though. He's addicted to weed, to the point he can't contemplate even one day without it. It might be nicotine he's addicted to, it's not clear. But your whole house will smell, he's getting arsey as you hoover up tobacco (that in itself sounds horrid) in case you hoover up his weed, he cannot contemplate life without it. Soon you won't be able to go on holiday anywhere nice as he won't go cos he's worried about where he can get some from when he gets there (Thailand is out, by the way).
Weed is the second commonest reasons that people present to drug and alcohol services now.
Not all weed use and weed smokers are the same, and once you get to the heavier dependent end, it's unpleasant, often does affect their motivation and mental health and is definitely addictive.
That doesn't mean all weed smokers have the same effect, or that no-one should ever have a joint, but for some people, already with demons and other addictions, it won't be a good life choice for sure.
Good luck OP, but I think you honestly need to get help to support yourself, don't worry about his family for now, they may be horrid, they may have been burned by his behaviour before. Just leave them be and concentrate on trying to fix the situation you are in, as I really doubt love will be enough.