Best option to fix cracks in ceiling with radiant heat?
I owned a Condo a few years ago with radiant ceiling heat, similar construction timeframe (I guess warm air fell in the '70s). We did not have any ceiling cracks, but skim coating or texturing the ceiling if you avoid screwing anything in should work fine, based on the experiences of others in our complex.

Our unit had had the heat fail in a few of the rooms, and we simply had wall heater units installed instead of trying to replace or repair the radiant heat. I don't think that the ceiling heat was worth the trouble, because at the floor, it was still always cold in winter, given that we had a ground-floor unit and weren't getting the benefit of someone else's ceiling heat.