Thanks so much to everyone who gave me suggestions yesterday! I bought a crate last night and started getting him acclimated to it (getting him to go in for treats and toys, feeding him meals near the crate), and I puppy-proofed my bedroom and then shut him inside for a few short periods last night and this morning. I forgot the bitter apple spray, damn it, but I'll pick that up today.
This morning I moved all his toys, both his beds (I bought two figuring the cats would commandeer one, but instead Buster promptly designated a daytime and nighttime bed), and the crate into my bedroom, and I played with him quite a bit before shutting him up, so I'm hoping I wore him out a bit. And I'm going to continue with crate training, and we start obedience training this Sunday.
Please think good "Don't be anxious, poor little puppy!" thoughts in his direction today? Also, think calming thoughts in the direction of my poor cats, who are not happy about being locked out of my bedroom where they usually sleep all day.