By gum, you've written a lot! What really strikes me (not that it's a new thing) is how central Buffy is to your thinking. You're like a modern Scholastic :-)

long, 2-3,000 word scenes are much more what I prefer to read, but it can leave other areas feeling very scant if you don't have much to say and only want a 500-word scene

Do you think so? (TBH, I'm not sure I've ever written a 3000 word scene myself, but I've written lots of one-line-of-dialogue scenes ;-) But, as a reader, I like the writer to concentrate on the meaty bits, and deal with the other bits as quickly and efficiently as possible.