Definitely sounds like yours is being more stubborn than usual. My '97 with about 15k miles came off without too much hassle using the autozone rental puller, and the bolts that were in the kit. They were the "yellowish" metal, suggesting the kit came with grade 8(as you'd think it should). Tightened it as much as the impact would get it, smack with a mini-sledge, repeat like 3x, on the fourth smack it popped off. No bent bolts or stripped threads.
You can get a 1/2 drive impact from Harbor Freight for $20. I don't use it that often, but it works fine when I do. Make sure your compressor has a decent air tank to it...mine is just a small pancake one, and I only get a couple seconds of use before the pressure drops off too much.
Don't worry, bring the puller back to autozone and tell them it broke, they won't charge you for it. You can ask about what other pullers they may have, but I wouldn't recommend the "claw" style for the reason mentioned above.
When you're using the bar between the three bolts and case guard to jam it, is the bar contacting the flywheel? Just wondering if with all that torque, the bar is being wedged against the flywheel, keeping it from popping. Maybe try putting the bike in gear, and putting a brick on the rear brake pedal?
