Thank you all for the great ideas! Update follows.
I picked the car up from the shop yesterday, and it ran better. Much less shake at idle. The shop said they didn't do hardly anything and that they don't understand why the car is running better, so they didn't charge me a dime. They said the pressures were in range cold and warm, so that's good, but I'll verify myself.
Took the car home, removed heat exchangers while it was warm because the nuts were easier to get off and because I didn't want to spill fuel on a hot engine. Found out the hard way that my oil crossover pipe is the wrong kind. Oh well, back on the old ones go until the right oil pipe arrives with a front fender kit from Elephant Racing.
This morning, I dove into the fuel system with the car cool. First, I did a test on the fuel pump to make sure it was delivering enough fuel: 2.25 L in 60 seconds, pass.
Just to make sure nothing weird was going on impeding flow through the accumulator and the filter, I tested again downstream of those components and got the same result.
Then, I started rigging up the CIS sensor. I attached it between the WUR and the fuel distributor by connecting to the WUR and the control pressure inlet at the fuel distributor, pulled the fuel injectors, inserted them in my six graduated cylinders, and (after a trip to a few stores for wires, connectors, an inline fuse, and a switch per the Bentley book's instructions) built a remote fuel pump switch I could use at the back of the car.
When I ran the pump, all six fuel injectors started leaking. AHA! Not good. At this point, I directed all my attention toward the injectors. I checked the CIS gauge a few times, but it read zero; I must have set it up wrong, will reread the instructions and rewatch the video.
More observations of the fuel injectors: only 5 & 6 had what I interpret to be acceptable spray patterns at
most amounts of flow. The rest were bad no matter what rate of flow I chose. They all dripped and squirted awkward, not conical shapes at low flows. See video:
https://www.youtube.com/watch?v=7mXIYztCpDQ
The amount of fuel delivered, happily, was extremely consistent. The greatest % difference at an average of 110.5 mL fuel injected per cylinder was 2% (range of 108-112 mL). The color of the fuel from cylinders 2 & 3 was much darker than the other two, however. I thought that might have been because the fuel injectors sat in the bottom of those cylinders. I re-tested twice, being careful to dip a few of the other injectors deeply in the fuel and switching fuel lines between 1 & 2 and 3 & 4, but the discoloration stayed at 2 & 3 both times. Conclusion: there is some kind of corrosion causing discoloration either in the lines or in the injectors at cylinders #2 and #3. (Replacing them all anyway, but in 10 years when I rebuild the engine it'll be interesting to see if those cylinders show different wear patterns.)
That took me all day. I replaced the fuel injector seals with new rubber even though I'll have new injectors installed soon, the old rubber was very hard and contamination in cylinder head = bad. There definitely may be other problems, vacuum leaks, etc., to be found, but this big issue with injectors is a good thing to have found. Still, tomorrow I'm going to throw the old exhaust parts on tomorrow and start checking timing.
I checked the fitment of the plate very unscientifically: when I put a light under it and looked in from the top, the light looked pretty consistent around what I could see. There was not a ton of room to get in there with a feeler gauge, will have to make some more room for myself there somehow.
Will attempt the CSV/TTS test suggested above. Another trip to the hardware store soon for a push button!
Remaining tests/things to measure:
-cold & hot system & control pressures (re-watch Klassik video for correct #s, my books don't have them for the '77)
-fuel distributor plate resting position orientation (centered, correct height)
-CSV (by wiring through TTS, need to find)
-ignition timing & dwell
-verify spark at all six plugs are sparking (bought a nifty in-line tester for $20, but if that doesn't work I'll use the light sensor on each)
-pancake-shaped AAV holds vacuum or not (the one passenger's back that's in line with the AAR)
-cylinder-shaped AAV works or not, vacuum leaks (the one just above the throttle)
-fuel pump check valve (residual pressure overnight from Wed to Thurs, using CIS gauge)
(For anyone trying to replicate the fuel pump switch who's as clueless as I was: the fuel pump relay is the big red cylindrical thing closest to the rear of the car in the fuse box in the frunk, and the terminals 30 and 87a can be identified by looking at the back of the relay. 30 goes to the pump, 87a is hot when the key is on. Connect a wire to 87a, run it to the back of the car, connect that to a switch, run another wire to the front again, inline fuse, into 30. Home Depot sells banana plugs that fit right in the relay holes, they're by the other stereo components and you just have to pinch them down a bit to fit them in.)
Again, thanks for all the support!