Chivewarrior, based on your description, I thought you might be in SF -- let me just say that I recognize completely the kind of family you are dealing with, and you have my sympathies. It has been colder here the past two weeks than I can recall in my nearly 10 years of living here, so part of it is that people just aren't used to it and don't know what to do. But your landlord family is being out and out cheap. It is utterly ridiculous for someone to expect you to wear slippers or heavy clothing -- it is almost always 65 degrees here, so that kind of winter clothing is not something most of us have.
If you can stick out for another month, that might work, particularly since it is supposed to get back closer to normal later this week. If you do need other options, you might also try Craigslist or some of the local colleges (USF, Hastings, UCSF, SF State and City College). No idea if they have resources available for non-students, but I had luck when I was in grad school with an apartment swap with a student at another school. Best of luck to you!