Answer from cs61c-ck (Allen Lee 16583554) for Question 2
By having pages of fixed-sized chunks, we can keep some of the implementation of virtual memory invisible to the programmer and compiler.  If we use variable-sized chunks (segmentation), the address space is split into the segment number and offset, which the programmer and compiler must be aware of.  Bigger chunks are good for protection and for sharing in an address space.  Smaller chunks are good probably because they are faster and take up less space.