1. What is the proper setup for multiple chips ; %1010x01x ?? or what?
I use the 24FC512 because you can have up to 8 devices on the same bus.
The 515 is a bit different,
I'll have a look at the datasheet and get back to you later

2. Are the external eeproms physically tied on pins A0 and A1 to set their address?
The answer is: YES

3. Do they all share the same bus lines?
The answer is: YES

4. What is the PBP command setup for dealing with multiple units? Does my program logic deal with EACH CHIP, or does PBP make both of them into one big memory bank, and I don't have to worry about the two units?
You can only access one physical chip at a time by specifying it's address with I2CWRITE / I2CREAD

5. If Do have to worry about the two units then I need to be intelligent about using one up, then jumping to the other, then remembering where I put things when I go to get them back.... Right?
You would need some pointer anyway to memorize which location you have last written to.

Have a look at this thread