Thanks all.
I got a new direct drive starter from Hillbilly Wizard. I put it in today and it works great. The truck still doesn't start, but the starter cranks beautifully and it makes no nasty grinding noises. I'm hating Napa right now. The flex wheel teeth I could see looked undamaged, though I didn't pull the cover to look more broadly. The picture below shows my $350 6-month-old NAPA starter, and the shim which I reused.
Here are 2 tricks for newbies like me. First, jack the frame up high enough that the front passenger side wheel is bearing no weight. That gives you enough space between the front axle and the frame that you can remove and install the starter. You'll need at least a 24" jack stand. All normal safety rules apply, regarding working under a car that's jacked up.
Second, the manual says to remove the bracket and disconnect the wires. Don't. If you do it that way you'll never see the wires without mirrors or an inspection camera. I loosened the bracket bolts, but left them in place. I then removed the starter bolts and slid the starter forward enough that I could see and disconnect the wires. The loosened bracket supported the starter while I worked on the wires. Then I unbolted the starter from the bracket and carefully lowered it. Installation was the same thing in reverse.
I still seem to have a fuel issue. As a test, I temporarily installed a 10PSI Webasto electric fuel pump between the filter and the IP. The pump runs happily enough, but the engine still doesn't fire. The starter cranks beautifully, though. I saw no leaks under the truck, after running the pump for a while.
Questions for the wizards: Should I be able to hear fuel returning to the tank? I was hoping to hear a trickle, but maybe the outlet is low in the tank? My tank is half full... Also, what are the lines in the pictures below? They seem to run to the fuel tank, and one is insulated. ???
I ran out of daylight. Tomorrow I'll try looking at the fuel system more closely. With the electric pump in place, at least I won't be burning up my new starter trying to debug my fuel system. Maybe I'll reverse the direction of the pump and look for leaks that way.