#1 only proto3 upgrade kits are in production and for sale. I'm not saying it's impossible to find an old stock PS2 kit, but they are pretty rare in 2024.
#2 the ENTIRE purpose of that kit- was to provide an upgrade path for PS1 engines.
#3 No, a Lionel universal AC motor (AKA pullmore) is not compatible with PS3 upgrade kit for 2 reasons-
A. no flywheel for the tach, and
B. the universal AC motor is not compatible with the DC motor control of the PS3.