Am I missing something on my final 2000 grit finish by doing
things this way? Might it be a better finish by going something like
400/600/1500/2000?

You're probably spending a lot more time sanding than you need to.

I can understand why this might be, I
suppose, with the micro abrasions on the sanded side, but I wonder if it
has
any impact on the resistance the finish has to liquids. After all, I'm
doing all this in order to protect the wood from occasional spills.

Try a coat of butchers wax. It'll make the surface less porous (easier to
clean) and restore the beading.