Pig, the answer to your questions are in the contract. Yes, you can pay for the New York hotel room as a part of your intl deviation per:
Chap. 25 - C.3.d.2.(b) A pilot who deviates from international deadhead travel may expense hotel(s) as part of his deviation travel as follows:
(1) he may expense 1 hotel room as a deviation expense, or
(2) he may expense up to the same number of hotel rooms as in
his scheduled deadhead.
And you can stop at an intermediate stop (i.e., NYC) for up to 48 hours as part of your deviation travel per:
Chap. 25 - C.4.d. Travel claimed as a deviation expense must begin or end within 3 days of the scheduled assignment to/from which the pilot is deviating (e.g. scheduled deadhead, trip or R-day) and must proceed to the intended destination of the deviation with no greater than a 24 hour delay enroute, domestically, and a 48 hour delay enroute internationally.
Just follow the normal deviation procedures and you should be covered. You should make sure you give yourself plenty of backups out of NY in case something goes wrong with your scheduled flight (maybe make sure a EWR-CDG jumpseat the night after your scheduled DH is available).