Tell the Dean of students that the Housing director said the only way you can get heard is if you file a disability complaint, which your lawyer will do since otherwise you have to drop out due your disability not being taken into account, but you wondered whether at least someone may tell you why your request was denied when your doctor specifically requested you had to have a single due to anxiety.
I think the Dean will hear you were suggested offhandedly to file a complaint for something you have grounds on and that a lawyer’s involved. And magically you’ll get a single.
Your major can’t be THAT rare.
There have to be colleges that offer it beside that one.