Finished, relatively quickly. An enjoyable puzzle, clever clues, nice theme. Got the theme from 21a when I hadcrossers from 13, 18 and 19 and could only think of one word to fit.
FOI: 17A
LOI: 16D
COD: 21, where I nearly googled for the biblical text, until I got those crossers: or 29a, now that I think about it!
I don't understand parsing of 16d (def is 1st word or 1st 3 words, but then ... ?) and 27a (last word def, ...?)