The good news (great news, actually) is that the insurance company is being great. They know there had been pre-existing damage from several years ago, and since they feel they have to tear out the old damaged material in order to deal with the new damage, they are covering that. Even better, since they have to tear out the old damaged material to deal with the new damage, they are covering replacing it.
Roto-Rooter came about an hour after I called, and cleared the clog, and I'm really grateful to them for the advice to call my insurance company. I'm horrible about dealing with such things, and I don't know when I'd have gotten around to it. They took care of a lot of the necessary things for me, and very quickly.
The dogs and I have spent about a week and a half in a hotel, on the insurance company's dime, while everything in the basement got torn out, and over the first few days of next week the upstairs is going to get cleaned to deal with mold exposure. I have to bag up all of my clothes and bedding and towels and such, all "soft goods," to be cleaned, and all of the hard surfaces are getting wiped down with anti-microbials, to be sure there's no lingering mold contamination that could bloom again later. I did a bunch of the clothes-bagging this afternoon, and will do more tomorrow. I had to stop when the Servpro guys were leaving, since they were going to help me carry Charlie's tank (she's my snake) out to the car, and of course I couldn't leave her in the car for long. keeyoo and family are kindly taking care of her until we can safely move her back to the house. Meantime, because of mold contamination in the heat ducts, the ducts had to be cleaned, which is a very impressive and loud process!
My boss is being awesome, too, and letting me bring the dogs to work. Leaving them all day in the hotel room might work, but it's risky, since I didn't bring their crates. And, the dogs are being amazing. It's been weird for them, to say the least. They're behaving themselves at work (understandably getting a little restless here and there) and managing great in the hotel. I've been leaving them for a few hours at a time here and there, and so far, so good.
As much of a pain as this is, I'm doing my best to look on the bright side. I'll probably have a lot of tidying to do upstairs, but I'll also try to get rid of some random stuff I don't need. And in the short term, the basement is going to be empty and unfinished -- but then I'm going to be able to design and build a brand new basement. Insurance should cover most of what I want to do, at least to restore the level of finished basement I had before. Finished main room for hanging out, finished guest bedroom, and "3/4" bathroom (with shower instead of tub).
And I'm thinking about all the Marriott Rewards points I'm racking up at the Courtyard. :-)