I Have a 260 that hated heat (70c+ it dies almost exactly the same as what your describing) once I got a rather OTT custom cooling system working I was able to get it heavily oc'd and play anything an still could i guess.

Might be wroth resitting the cooler and testing it on other games at full load and such, see if it can be reused as a sub card or to run a 2nd/3rd screen.