No offense, but you don't have to be male or "some car expert mechanic guy" in order to read the owners manual. Mazda even throws in a CliffsNotes version -the "Quick Tips" booklet- in case you find the full manual to be a bit daunting. That said, here's your situation as I see it:
1. Mazda is not responsible. The filter cover/housing cracked because it was over-torqued. And it's not a design flaw; BMW and others also use a similar design- in BMWs case for over 12 years. It works fine if the tech has opposable thumbs and a middle school diploma.
2. Goober the oil change dude caused the crack, but he -or his attorney- will argue(correctly, I might add) that you had a duty to mitigate any damage by switching the engine off immediately the oil pressure warning light came on. The fact that you saw that warning light and continued to drive the car until the engine seized makes you ultimately responsible for any damage that occurred after the light came on, which is to say almost ALL of it.
In any event, it sure wouldn't hurt to discuss the matter with an attorney, but I'll be extremely surprised if you recover much of anything. Good luck regardless...