You have to pick:

I laughed out loud for a whole minute at the mere thought of having the excrete a crab.

That would actually be pretty awesome

Do I have to brush my toe teeth? Is there special toothpaste for use on the foot?

I think you probably would have to brush them. Although they wouldn't get as much on them as normal teeth, so perhaps they'd be ok. Maybe just careful washing when you normally shower would be sufficient.

Whole or like in pieces because i excrete crab all the time if the latter is true

Whole.