My 7 is back in action. Reflashing with stock rom brought it back from the dead, and I've put in an updated "RAM cleaner" app that somewhat improves usability (still reliably slows down and randomly reboots, but a lot less frequently).

Two main ongoing (apparently related) glitches seem to be wifi and "system ui", which typically crashes about ~15-mins after starting anything using wifi. If it makes it through a system ui reset without rebooting itself, it actually runs smooth for a few hours. So usable about as much as I need it to be.