Gitto - go with your gut re 17a - the across letters do look strange but do ultimately make sense (not that i have figured out the endgame)!
30a - wp = concatenation of two abbreviations, defn is first two words
23 - wp given by first 3 words, defn = last two words.
i have all the extra letters i think, but am struggling to fully trace an instruction. i get so far, then it breaks down.
I also havent figured out the relevance of the down side.
However am enjoying the puzzle, its certainly different and is proving a tougher nut to crack than recent weeks.