At least you have an aisle seat, even if it's in the back of coach.

AFAIK standard DL response if you can't get PS on the flight or be rebooked in Premium Economy on some satisfactory substitute TATL flight would be refund of fare difference (assuming that they have historical fares for award tickets, you might want to investigate the coach cost in miles of your dual inventory PS award ticket, so start by documenting the fare code for your ticket) plus a $200 apology voucher.

Try to search for alternate flights (ideally on JV partners or at least SkyTeam partners) and be ready to tell the phone agent how you want to be rebooked. Have the details (carrier, flight number, airports, scheduled departure and arrival times) for several alternatives available to tell the agent.

Some people report success in clicking something like change flights on the website or app (try both--they can give different results).