I see that the pumps are assembling machines, that they are actually 'creating' water (produces exact amount of water every second) instead of 'pumping' water (variable amount of water per second). Is it possible to change the type to pump instead of assembling machine?

It's impossible to set any energy consumption to real offshore pumps.

I was thinking that a regular fluid pump with infinite water source could be used, but I'm not sure

The regular fluid pump has no infinite water.

What is possible: do the recipe 60 times per second. Con: you cannot use beacons, 60 calculations per second is a limit.