Hi, Farr: I've just got up here!
15a Synonym for bad + abb. for book, all reversed, =archaic word for speed (in Ch. of course)
15d Def. "befit" (ONE word); busy animal surrounding abb. verse after 2-letter word for stop
28a It's one of those "hidden consecutive jumbles", extra letter P, def. "hot" ("brittle is the anagrind).
And btw all the letters you have already are correct.
Good luck!