Irfp250n n channel mosfet gate charge problem?
If you're wanting to use the Uno to control high voltage AC devices, I'd recommend using a relay for switching instead of a MOSFET. Relays are more reliable and safer, but don't offer anywhere near as fast of switching speeds as FETs, so for a simple light switch it's likely a better option.
in the datasheet the absolute max for Vgs is 20V, so it's no wonder why pushing 100Vs through it got wild. Relays isolate the two circuits so you don't run the risk of damaging your board or popping another FET. Even though the IRFP250 is rated up to 200V VDS, expecting it to handle the resulting Wattage would require a serious cooling system and lots of additional safety measures built in. As others have pointed out though, you probably should hold off on working with such high voltages until you have more experience.