Almost a 'draw', but I'd have to go with SA on this one, a decent response from them to a troubling thread, no clear winner. Loose valves could be a contributing factor to broken stud, hard to say. At any rate, the installer should have checked valve adjustment before startup and immediatly after 'run in' to verify, sounds like that didn't happen. Fel Pro gasket leak, man, I hate when that happens! What are you gonna do, like you have control of the gasket quality? Change brands? I'm not sure that gaurentee's a solution either, but it does serve as a warning, Fel Pro!
What a nightmare...