All done but I can't see what the two-word anagram of the 7 letter entry (defined as Huntsman) at 18 might be - Azed says it's "a proper name that may be verified on Google" but I can't find it. Anybody found it? Is it (2,5) (3,4) or something else? Cryptic part of clue is "rent troubled , reverse of low" so it's pretty obvious what letters are involved even if I didn't already have the huntsman!
I think there's a mistake in the special instructions - 18 is as straightforward as you outline above and no proper nouns involved! There is a footballer with the surname of the huntsman but that, to me, is irrelevant.
I read the preamble to mean that huntsman is the proper noun and the two word anagram thereof, net room, can be verified on line (it is not in my edition of Chambers)