If you have 2 S/C's as well as a parts car, It would be worth investing in the factory manual(s)
EVTM & the main book. They will answer most if not all of your questions & help you understand the systems & how
they work together, but are seperate. Brake boost/charging system vs ABS system. ARC system Vs variable assist steering, etc.
If your ABS light is on, your system should have reverted to conventional & won't work. How have you verified it is working-tried hard applications in loose sand,gravel,snow,wet surfaces & heard/felt the system activate?
I'm not aware of a seperate "proportioning" valve in this system, its all integral with the metering block on the master cylinder as far as I know.
So not sure what you replaced, unless it was that tee fitting for the ARC pressure switch.