Great feedback and suggestions, everyone. I really appreciate the input. This is keeping me sane -- hearing that it is actually possible to get this bolt out and avoid buying a new engine.

I've got four of the narrow Dremel aluminum oxide grinding stones on order through Amazon since my previous bit was the only one in stock at the local hardware store.

http://www.dremel.com/en-us/Accessor....aspx?pid=8153

I think I'll see how far I can get with these to start with.

DMC5180 -- Thanks for the additional detail on your drill jig setup. This sounds much more doable than the "DIY drill press" that I was trying to imagine. I'll give something like this a try if the grinding stones don't cut it. BTW, I think I was able to grind out and past the broken extractor with the first stone that I used. It is a little hard to be sure, however. The grinding stone sort of polishes everything in there and all the surfaces are more continuous and flush with respect to each other.