will these work for my game ZERO headset?

The game ZERO headsets share in the same basic shape but do use leather ear pad/cups to provide the closed ear cup sound design. I am unsure if these will work properly for you. They are made for an open ear cup design headset like the ones listed, G4ME ONE, GAME ONE, PC 363D, PC 360 & PC 373 D Headphones.

Do these fit momentum hd1 2.0?

No, does not fit momentum hd1 2.0. Sorry, don't have part #

Will this fit a PC37X?

Hi there, look it fit 100% in my GAME ONE headphone but realy dont know if fit in that one u need sry.

How is the heat retention with these over long periods of time? Should I expect to be sweating like crazy around my ears with these?

For gaming, they are fine and might trap less heat than the typical pad, but they are also meant for open-back sets. I've never had a problem with heat or sweat. I can't imagine it being an issue unless you're out exercising or in direct sun. More than fine for long hours indoors gaming, though.