I actually just finished going through it. I had done a large number of those tweaks, I did the same as you with the Keep WiFi on, didn't notice a difference when I toyed with that setting a while back. I did turn off hotword detection, so we'll see if that helps. I also saw someone mention the pedometer was draining theres. As I use the pedometer on my Gear, I didn't realize the device still had the pedometer running as well, so I disabled that. Can't think of too much else to mess with, but we'll see if those few small tweaks knock that Android System and OS drain down.