Welcome to the RV forum! I have a 98 Dream and had to re-do the stitching on the slide out awning using sail thread purchased at West Marine or equivilant.
The rivets have to be drilled out, but secure a vice grip to the awning core to prevent it from spinning out and possibly causing serious injury.
Work from the cap at the front of the coach and count the number of turns so the spring can be rewound to the same tightness.
This might be a good time to replace the rusted lock screw holding your awning material installed by Fleetwood with a stainelss steel screw...in fact repalce all those rusted screws while yoour're at it if you haven't done so already.
Let us know how you make out.