Fastest possible memory copy between 2 12ns SRAM DIP chips
"I would like to build a retrocomputer,"

So the question isn't about the "fastest possible" solution but about how to get a whole circuit humming along at a reasonable 32MHz or so...

Consider wire-wrap on protoboard instead of breadboard (with soldered power supply and decoupling, and good ground connections or even a ground plane) - easy enough prototyping and a whole lot more reliable - and "in period" so to speak.

To answer your specific questions : 

1) No additional time at all, if you are using them correctly (and counting in powers of two) - 163s are synchronous counters, not ripple counters like the 7493.

2) See the datasheet. If you have questions about that, ask for help.

3) Yes, you are starting to build a "pipeline" which allows one stage to work on the new address while another uses the previous. This is how it was done. With a good understanding, you should be able to get away with 25 ns memories instead of 12 ns at these speeds. Draw timing diagrams, from the datasheet values, until it looks as if it should work.

4,5) N/A