your graphics card should be set up to turn off if it gets above the danger temp, and that should be either mandatory or slightly configurable in the driver or bios settings for it.
if its not in danger, running hot is fine. You can check its fan, make sure it has good cool air supply. If its overclocked, turn that crap off.

the game seems to lack an optimization pass. The crude graphics (not a diss, but in truth, they ARE crude in terms of polygons and textures) should zip along without a lot of horsepower; its not a lot more intense than like wolfenstein 3d that ran on a 1MB graphics card in 1991. More pixels, due to screen res (and that matters) but all in all, it shouldn't be that big a pull.

try some external settings. Limit your FPS for the game to 35 or so. That is as good as original TV/movies. You can also try other external hard limits, but that one would help.

your card is towards the end of its life ... its an older card and even the 8gb version is still falling behind. If you can afford it, a new one may be helpful, but this game shouldn't require that.