35mm/36 exp is the same area as 120, 4 sheets of 4x5, approx 2 sheets of 5x7, or one sheet of 8x10 (they all fit in the same size file page), and 220 is twice that.
Presoak is a good idea to prevent uneven staining.
You might be able to get 5 rolls at normal contrast or minus development in 1500ml, but why take a chance with that much film? PMK is cheap. You could test one roll and see how it works.
General suggestions--you can skip the afterbath, particularly if you use an alkaline fixer, which is recommended. Gordon Hutchings himself no longer recommends putting the film back into the spent developer after fixing.
Pyro: why?--I like the highlight details and sharp look. I usually use ABC for larger negs and PMK for smaller ones. PMK seems to have a better grain-masking effect, but a higher level of "background" stain.