Hey, just wanted to share our experience, as it was very similar to yours.
My husband is allergic to some dogs. Like you, we visited our dog a few times with no issues, but once we brought her home his allergies flared badly and it was pretty miserable for him. We actually took her back to the rescue centre with the intention of rehoming her, but my husband just couldn’t go through with it.
What followed was a really tough few months for us - lots of discomfort and stress - but over time things did improve. These days he doesn’t get symptoms from her at all, unless he’s been away from her for a long time or it’s peak hay fever season (the doctors explained it like an “allergy threshold”, where other triggers can tip things over).
We saw doctors and allergy specialists and put a lot of measures in place: HEPA air filters and a good vacuum, keeping her mostly in non-carpeted areas, restricting her to certain parts of the house (not in the bedroom or upstairs, so he always had a refuge), plus regular baths and grooming, and washing all her bedding at least once a week. All of that really helped.
I’m not sure if this will make you feel better or worse. But for us, there was an adjustment over time. I do think people can adapt, but it’s also important to be realistic: it took A LOT of effort, consistency and money, and it was pretty intense for a while. That’s definitely something to weigh up too.
Also… your husband sounds like a massive dick. Absolutely nuts that he is treating you like that.