Cheers, Conan!
Yep - my R-400 has a vinyl cover, and if the WB-100 was staying with me, the first thing I'd do would be to get one made for that, too. Really it would be to protect the tolex and keep moisture out, but I'm like you - the sight of big glass bottles through the grille makes me slightly paranoid.
I guess it is paranoia - guitarists lug these things around all the time without giving it a second thought.
I suspect the feedback switch will make more sense at volume. I left it in centre (rock) position most of the time, but during rehearsals I tried it on the 'pop' setting and it felt tighter, almost solid-state. Possibly useful in a boomy room, or at louder volumes.
The 'Funk' setting didn't grab me, but I didn't really spend much time on it. Maybe it's a slap thing?
Enjoy the rehearsal - don't forget to pull the bass back if you need to, and go easy on the contour (at first, anyway).