We also had non-refundable SXM tickets for this November. When I called Delta a week or so after Irma, they redeposited hubby's reward miles back into his account without a fee. I agreed to a credit voucher for my own ticket, rather than a cash refund, as we are flying to a cruise out of Seattle next June and I needed a ticket for that anyway. So they allowed me to rebook for SEA for next June (even though it was a little over the allowed limit of one year since our initial booking) and they put a credit for a little over $200 into my Delta account d/t the lesser difference in price. I have a year from now to use that additional credit. We travel a lot, so that was fine with us.
The important thing to take away from all this is to be persistent and to ask to speak to a supervisor if needed. I had to in order to get them to extend the 'one year limit' on my initial ticket, even though the difference was only a mere 6 days. Ask nicely, of course. Patience is the key. The initial reps you speak to don't always hold all the power to give you what you want/need, so a supervisor can often help further.