AND, I expect this is the temperature of the inside wall of the calorimeter box. Not very hot. So maybe you should not worry about the insulation temperature? On the other hand, if the bubble foil falls off the wall onto the reactor (which is at 363°C), that might be a problem. I suggest you heat some metal up to ~363°C and hold a piece of bubble insulation up against it to see what happens. I expect the plastic will melt, but maybe nothing bad other than that. The stuff is probably engineered to avoid fire hazards.
Mostly worried about the insulation falling off the inside of the lid and onto the calibration cylinder. I may drill some tiny holes and string wire across the top to hold insulation in place. A fan failure could also cause dangerous problems, so I will install a thermal fuse in the box somewhere to cut power to the heater if it gets too hot where it shouldn’t be.