Hello!
I am very interested in this topic. I have been studying gameplay difficulty curves for a while and the ones in game & watch games are pretty awesome.
When I opened my precious Mickey a while back, I indeed saw only one chip. It's cool that you went into a lot more details.
Did you manage to see how the 'waves' in Mickey are timed?
They start with one egg, then 2 etc then reset at 100 I believe and more eggs start to come and speed up.
Did you see this in the code? I would love to study this. If you have a disassembler I would love to look at that code (I'm a z80 msx guy but I have done GB, Amiga, Genesis...).
Cheers!
Fred.