A good quality (and properly installed) heli-coil will be stronger than the original threads. Even so, there is hardly any force applied to those bolts, the caliper simply slides on them.

 

It's my DD so I had to put the new hubs and new brakes on and give up on it for now. I got a heli-coil kit to fix the brake caliper mount on the knuckle. I've got a new knuckle sitting in the garage so I plan on getting some bigger hammers as suggested and trying again with extreme prejudice! I guess my 2.5lb hammer with a long handle wasn't close to enough from the sound of it! This is the first time it hasn't been big enough...but it's not exactly huge so it was bound to happen. Thanks for all the suggestions everyone!