The Nikor will hold more film (12 sheets) than the liter of developer is rated for. Every other slot is a good match for chemistry volume to emulsion area.
Depends on the developer and the concentration. The Nikor tank uses 1200ml for 4x5". I don't have any trouble with Acufine (stock), ABC pyro (1+1+1+12 is what I usually use for 4x5"), and I think you would be fine with D-76 stock or 1+1 and maybe even 1+3. I'd be concerned, though, about Rodinal 1+100 or PMK 1+2+100.