Thanks for showing your progress!
It appears my '99 started off in similar condition to yours, though my interior's a bit more ratty. I did not know that was the AHC tank by the firewall on DS. Mine is filthy black and I thought it was going to be either brake or power steering fluid, but obviously hadn't done any research into it yet. I'm having a slight issue with AHC that I'm going to look at addressing soon: front end drops to Low position if sitting off for more than a couple hours, but pumps right back up on start-up.
Did cleaning the MAF sensor and throttle body help with your MPG? I'm only getting 10-11 around-town right now, but it appears most people on here are at least 13, and I've been trying to drive a bit gingerly to see if it makes any difference.