Firstclasser, here's how I understand the situation:
Husband AMD-JFK on 4th Oct. / JFK-AMD on 15th. Jan
You JFK-AMD on 15th Jan. / AMD-JFK on 10th Feb.
The problem is that on the JFK-AMD you are not booked on the same flights (for both JFK-DOH and DOH-AMD legs) and your Husband has a long connection in DOH and won't even enjoy any of these fabulous bottles at Al Mourjan lounge
The first good news, is that change fees for India originated ticket (your Husband ticket) are usually low (something like 80 USD).
The second good news is that if you change a ticket after departure (after your Husband flew AMD-JFK), you will benefit from history price (the Travel festival promotional price) instead of having to pay the fare difference with actual price.
So, if you want to minimize the change cost, I would suggest you to wait until 5th Oct., after your husband flew AMD-JFK, then request for the change, crossing finger that there will still be availability in the same booking class (I) for the same flight you are booked on. If there's no I class availability, you would have to pay the fare difference or you can wait for availability to open in that booking class, even until to 1 or 2 days prior to the flight (if your nerves can stand it and if ending up with not changing the ticket is something you are ready to accept if you can't change it at a good price), when, if the flight isn't full, Qatar might open availability in all classes to fill the plane.