Well that's what I needed to know . . . that you hadn't started with Whitedog's methods. I would first :
touch the end of the torx that fits to a grinding wheel. This will sharpen the very end of it so it can hopefully get a bite on the very bottom of the torx screw's socket.
Then after heating the assembly in hot water or perhaps with a soldering iron tip, filed to get down into the recess if needed . . .
if you happen to have a drill press you might want to put the torx bit or a cut off torx driver into the chuck of the drill press and use the drill press to hold the bit very firmly into the bottom of the torx screw. Put a stop on the drill press table to keep the knife from turning and then put a wrench on the torx bit (it's a 1/4 inch wrench) or put a pin in the chuck on the drill press or what ever else you can to use to turn the torx driver while it is in the chuck.
Failing that, if you don't have a drill press or other press to hold down on the bit you could gently put the knife and the bit between vise jaws and turn the bit with the 1/4 inch wrench. I have done that quite often with cut off pieces of allen wrench. Do you see what I mean ? The vise jaws hold the bit into the screw and won't let it rise out of the screw. Works great. As long as the screw head isn't too far gone. And the end of the torx is ground flat and sharp on the end..
It goes without saying . . . be sure you have the correct size torx bit before you attempt this.
Realize you have to loosen the vise jaws gradually once the screw begins to back out of the hole.
As far as the rubber band to fill the gap.
I would recommend steel foil instead. Super thin stuff. You can get it as shim stock. I have never done that but the rubber band is hopeless; it is going to take something very thin and solid like steel foil.
