Aren't the screws T-35? I thought they were... I know I blew up a couple of Torx bits because I was using the next size down accidentally. The only thing I can really say is maybe some PB-blaster and vibration will help - and make sure you are applying rotational force ONLY, and as perfectly on-axis as you can. If you don't it increases your chances of breaking the bit a lot.
If it really comes down to it, you can use a Dremel to grind a large notch all the way across the top of the head and use the largest flat blade screwdriver or bar stock you can find. I had to do that on one screw holding one of my door latches in, it worked great.