How to remove a frozen rusted bolt w/ broken bolt extractor inside

I replaced the a/c condenser in my Camry, but in teh process of disassembly, I broke one of two hold-down bolts for the radiator. It was rusted, so I doused it with WD-40 (all I had), let it sit, then clamped on vise grips. SNAP...twisted the head off.

So I went to the parts store and got a bolt extraction kit with the reverse-threaded flutes and drill bits. I drilled the hole (acually went all the way through the rusted bolt by accident), again with multiple shots of WD-40, and inserted the extractor. I used a crescent wrench and proceeded to snap the extractor bit, leaving the tip embedded in the rusted bolt.

Now what???

The extractor is a harder grade steel so drilling will be very difficult and likely to wear out any drill bits I use. And I cannot access the underside because the front radiator support is a box channel. I could try to drill small holes around the broken tip, but the drill bit size needed would be small enough that if it caught on the tip, it would snap as well, making things worse. And I'm not sure that the metal thickness of the support would be thick enough to drill a new hole for a sheet metal screw...plus that would look weird.

I'd appreciate any suggestions...thanks!

Would it be possible to drill a moderate sized hole on the opposite side of the support to access the back of the bolt? If you really find you have to weaken the support, you can weld some thick sheet metal or plate over the hole to re-strengthen the support afterward.

(WD40 is not a penetrating oil, for your purposes. That may be why you didn't free the bolt originally. PB Blaster may help with future attempts.)

Accessing the underside of the bolt would require re-removal of the a/c condenser I think...meaning discharging the a/c system. I could drill a hole to access it from the side (either engine bay or front grill side) though.

I've also read that one could weld a washer to the broken stud, then weld a nut onto the washer and try backing that out. That'll keep you from welding to the surrounding metal and will also heat cycle the bolt, helping to loosen it. Now I just need to find a washer, a nut and a MIG...thanks!

You can buy a tungston carbide steel drill bit the same size as the drill you drilled all the way through. I have purchased them on ebay. It is the same as a concrete bit tip but is held in a lot better.
I drilled one out of a Toyota crank shaft years ago a rough job.
Can you drill a hole beside it and use a bolt and washer. Usually they have enough room to drill beside it use a large washer to cover the damage and use a new nut and bolt. If the metal is thick enough drill and tap a new hole use a big washer. The idea is to hold it in place and look like a decent job was done.

I might have some WC bits, but haven't been able to focus on the car at the moment. I just have to drill into the extractor enough to where the taper is smaller than the hole diameter...should push right through after that I think.

Unfortunately, there's not enough metal there to tap a new hole. The bolt is held in place by a nut welded on the underside (inside the box channel) of the top sheet metal. Drilling next to it would break the nut. Thanks for all the ideas!