Thanks for those tips. Managed to fix the problem!
Good news I am not fucked!
So after blowing out my comically gross case I put the machine on using the mobo gpu. No problems. I plug the Radeon card back in (with MSIAfterburner on) and find problems start basically immediately as the fans start spinning. Theory becomes that the fan is spinning so hard and the card is so overweight that it's jiggling itself loose from the mount.
Another few pounds of air to even more thoroughly dust the filthy card, and some more effort to make sure it's mounted properly and securely I start the rig again and notice that Radeon's gamer optimizer stuff is on and trying to optimize shaders for the card. I turn that shit off and it works without problems even when I use afterburner to spin up the fan to max speed.
... So basically radeon's optimization stuff managed to completely fuck my rig for a while and I was a dope for not noticing. OR... I managed to go for 3+ years with a crappily mounted graphics card and just now fixed it to no immediate detriment!