I believe I may have finished this puzzle, but I have been unable to parse two clues. The first is 13 across which, if the rest of my reasoning is correct, will provide the third letter of the first word in the second nineteen-letter set of words. The second is 25 down, which provides the penultimate letter of the third word in the first set of words.
Any hints welcome, or alternatively, please let me know if I am barking up the wrong tree.