Update 11/14/17:
So the main problem I had was a small valve on the aft plumbing panel. It's a two way (90 deg) valve that directs city water either to the fresh water tank, or to the overall system. After reading the plumbing drawings I figured out that this valve must be in the wrong position.
Looking at the valve, it was pointed at the right place, but as it turns out the valve was installed 90 degrees out of alignment. So while it was pointed to "fill system" it was actually filling the fresh water tank. Hence all my air blowing out of my gravity fill. When I turned the valve AWAY from the label for fresh fill, it worked like a charm. Ugh. So much time wasted. And of course, none of the instructions or YouTube videos talked about this little demon valve.
Additional details: I never did find a HW heater bypass, but the drawings say there is one (only one, not three, which is weird) but I know it's behind the panel that was blocked by my fresh water filter system. So again I elected not to go with the antifreeze.
I was able to order the appropriate bypass valve for my Shurflo QL3 filter system. Pressurizing again with air I was able to blow out the little fresh water tap on the sink. I then did some research and found the correct jumper points on my icemaker (also fed from the Shurfuo filter) and energized the fill solenoid, and air came out of there too.
So now I'm reasonably happy with my winterizing. I've installed a trickle charger and I'm also running an oil-filled radiator set at about 45 degrees for those really cold nights. Also got a boatload of DampRid around.
It's amazing how much you learn by doing.