I spoke with the Service Director at the dealership about the situation today, requesting for corporate mazda be made aware of it in case the engine failed prematurely. He offered to make the situation right and that I could bring in the vehicle at any time and they would put the engine thru a pressure test and check inside the cylinders and headers to make sure nothing was damaged and also give me a few free oil changes . He also said he would go after the tech that over-torqued the gasket in the first place. Basically, "this should have never happened. we'll give you a loaner car while we make sure the engine isn't damaged, and if it is damaged we'll make it right". So, that's pretty cool.
However, I'm not sure if I want them performing the oil change again...
Responding to bold/italics points in order:
1. Don't trust or count on this dealership's service director contacting Mazda on your behalf. You can do this yourself; read the warranty booklet that came with the car - it has procedures and phone #'s/contacts to call when you are not happy or otherwise disagree with how a Mazda dealership is handling a problem. The best you can expect to get from Mazda in this case is that you would inform them of the incident caused by their dealership's incompetence, document the miles on the car at the time, and they could extend your warranty on engine specific failures.
2. Other than offering you a few free oil changes, the rest of this is pure BS to try to appease you. There is no easy way to determine if damage was done, short of doing a complete engine tear down, inspect/measure/spec every moving part & reassemble the engine. He's smoking crack if he says otherwise. Besides, who would pay for all that labor? Mazda won't, because your engine hasn't failed, thus no valid warranty claim that the dealer can charge to.
3. Did the dealer actually say/document that the gasket (i.e., drain plug) was over torqued? If so, then when calling Mazda corporate, I'd request that they authorize a DIFFERENT dealer to inspect the oil pan, and if it's damaged, replace the oil pan free of charge under warranty. Reason is if the dealer over torqued the plug to the extent that several quarts of oil leaked out, it is
highly likely that they damaged your oil pan - the threads for the plug could be stripped, and area around it (that the washer seals against) could have been distorted. In their repairs they did to get you back on the road, they could "fix" it and get it to seal by using a little thread sealant on the plug, and torque down the new gasket/washer just a smidge tighter than spec to get it to seal up, but that is NOT a permanent repair. A few oil changes later, and you'll likely find that the plug threads are too stripped or oil pan mating surface too deformed to seal, requiring repair.
4. I would not go back there. No excuse for F-ing up an oil change!