The difference here seems to be that you’re a recreational user while he’s an addict.

His reflexes are fried. His kidneys are being maxed out. Him sipping on poison all day is tearing his GI tract apart, hence the vomiting.

Your body forces you to vomit once you have over dosed yourself so it can lower the concentration of whatever toxin is in the blood. These little accidents of him hurting himself is bc he has impaired senses and judgement.

He needs to stop. Give his body a rest. If not, if he refuses, you have a decision to make - you’ll just have to put up with him getting sick and hurt a bit more and more with every passing week as he gets progressively worse in his addiction OR … Leave

At his rate, and without stopping or getting help, unfortunately addicts succumb to their addictions in some way. OP, down his path, sadly his days are numbered.