Should II rehome my cat?

So I’ve had him since he was a baby. He’s turning 4 in June. I love him so much and we’ve always had a special bond. Since having two kids he does get less attention but I’d like to think he’s still happy. He’s a very fat cat. He got fat after his neuter so he’s like 30 pounds now. He’s fine, has regular checkups and is on a diet from the vet but it’s not helping, he’s just a big boy lol. Anyways my husband has been having breathing problems for a while. So bad to the point he’s ended up in the hospital. We thought nothing of it, just that he smokes maybe that’s why. Well we just found out he’s allergic to dander I guess. Which makes sense because my cat has A LOT. He has a special spray for his dander but it doesn’t do much. So my husband is at the point where he constantly feels sick and needs an inhaler to breathe. Is there any medicine that could help that severe of an allergy? I’d like to add, he has a problem with addiction. He can become addicted to anything very easily. Hence the smoking weed and vaping. I just really don’t want to get rid of my boy :( I know if nothing works I will have to but I seriously don’t want to. Has anyone had this issue and been able to keep their cat?? Or should I rehome him? Ugh this seriously sucks and I’m so sad. I’ve had him so long and he was my boy long before my kids came along.

Thank you guys! I’d like to add that his issues starting after we moved in together, I had my cat before we lived together. But we didn’t think it was allergies at all. And he did quit vaping for a long while but never improved so started again. And it’s been confirmed allergies so we have talked to the doctor but she said to take Benadryl 🙄 our doctors don’t really care and he won’t take it because it can become addictive

So it turns out his allergies are causing severe asthma but he does not want to rehome our cats. So I guess we are trying some tricks from the vet first. If all else fails then his health comes first.