I am allergic to dogs, and I have allergy related astma. I take antihistamines (or do you call it hystamines in english?) every day, all year round, use my astma inhaler every night. Keep the house clean and groom the dog outside, every day. I just wanted you to know that I think it can be done, does not have to be impossible.
Of course there are different degrees of allergy, so I can't speak for yuor OH. I'm even more allergic to cats than to dogs, (my doctor said woooow omg! when she read the test result on cat allergy, to give you an idea) and every time I come home to my parents house for the summer, it takes me several weeks to get used to the cat. But it gets better at the end of the summer.
I've heard good things about petal cleanse. The one where you wash the dog/cat every week. It is supposed to remove the allergens from the fur. It will take at least two weeks before you see a result, because it takes time to get the allergens out of the house. (or so I've been told). I haven't tried it yet as I'm fine most days. But I'd love to hear if you think it works

I hope it does! Must be frustrating at the moment with your OH getting worse. Hope you find a good solution!