I am wanting for safety a uC to determine a few environmental checks before a device is allowed to be activated, it is a relatively low voltage (2V) however high current (4A) load (powered by a beefy constant current regulator)

A relay requires some current to initiate and inductive kickback protection on the uC's side, so I do not wish to implement something such as that if there are other options. I had looked at some power nFETs to do this instead and do not understand some points.

Will 4A flow through the power nFET even though it may be located after the load? A simulation (i.e. falstad) shows current being the same before and after the load and through the nFET. If this is true, I will have to add heatsinking, however does not make much sense to me as the load will "use" the 4A mostly?

Can the nFET allow 2V to flow through it without much trouble when switched on by my uC, i.e. is without too much resistance?

nFET something simple like this: <http://www.fairchildsemi.com/ds/FD%2FFDPF5N50T.pdf>