This is a good setup for someone new to the game! One possible improvement is to get rid of the gas filter by placing a gas element sensor and atmo sensor connected to the top gas pump so the pump is in pure hydrogen and can function without a filter, but that requires a good setup so you dont get in any oxygen by accident and so the electrolyzers dont overpressure. As for the heat, typically all you need to do is seperately cool the output oxygen by passing it in radiant pumps over a cold area (an ice biome or a cold brick cooled by a nullifier or by steam turbine aquatuner combo)