propspero, if I may offer some minor observations without being too spoileresque:-
- the word you think is second, I think is third
- NAIN needs a couple of letters before it and one inserted into it to make sense
- the CASTODY string you have found does not have a C in that position, and is missing a letter towards the end; and once resolved you'll see that this particular string of letters covers half of the words in the final phrase