Increase re-heating oven temperature for cooked ham

Yeah, 25 degrees extra shouldn't make a big difference to dryness. If you have an extra roasting bag, that'll help it stay moist. A gas oven will give you more moistness than an electric oven and you might get away with an even higher temperature. I doubt it'll make a big difference to the total time, though. In an emergency, the easiest way to quickly heat a pre-cooked ham is to slice it and use moist heat on the slices.