You are NOT going to drill an EZout. Too hard. You CAN try to BREAK it out using a punch. Usually, you can at least loosen it up to the point that you can get it out with a magnet.
For the hole with the bad threads, I suggest a heli-coil or similar thread repair. Makes a good long term repair.
In every case that I have seen, engine mounting bolts do NOT go into the crankcase. Consider...a broken or loose bolt would become a MAJOR oil leak in an instant. That would be some pretty lousy engineering IMHO.