From your references to the manual we are talking about a 94-95?
I will base my suggestions on the 94.
all fuses that should be hot at all times are dead
S276 goes back to MAXI fuse 11 under the hood. You did not state that you checked it.
locate S276 and check that splice to see if power is present there
Before you do this check the MAXI fuse 11 is passing power. (test light on both fuse pins should light).
If the MAXI fuse 11 is OK check the other legs of the splice 276. Do you have power on the two ignition switched fuse banks? In acc and run 6,7,11,15,14,(12 RM) and 24 . The other bank is run only 16,18,17, and 20.
If you do not have power on 35,33,34,27,28,26,29, and 30 but the other two banks have power in run you may have a splice fault.
I checked continuity between the dead fuses and connector C207 and they all ring out.
Bad contacts can ring out but fail under a real load. I am a electronics guy but I do most tests like this with a test light as a multimeter will show voltage on wires that will fail to light a test light.
If you do not have power to all three banks AND you are sure the MAXI fuse 11 is good you may have a wire problem between MAXI fuse 11 and the splice. Use C207 to split the problem.
You are unclear about when it does not start. Is it cranking the starter and not starting or is it not cranking?
There is a lot on mixed information on the VATS system.
A new key (your spare) should measure the same across the key pellet as at the the plug to the lock cylinder at the column. Where wht/blk and ppl/wht plugs into the (orange?) wires that go to the lock cylinder unplug and test the wires to the lock cylinder with the good key(ohm reading should be close to the key value). A worn out cylinder should be changed out before it causes other issues. You should get the same reading at B7 and B8 when you unplug it from the module.
Quote the internet: the only person VATS stops from starting the car is the owner.
I have read that if you unplug the lock cylinder from the VATS the VATS considers it a malfunction and lights the PASS KEY FAULT. The internet says you can still start the car. The internet claims thieves cut the key sensor wires and break the ignition to steal the car.
The only real VATS test is to check the VATS outputs.
PWM (A3 DK BLU) some meters will see this as a AC signal but it is a pulsating DC (40-60 Hz). This allows the injectors to run.
A "ground" (battery to) on A4 yel/blk grounds the Theft Deterrent relay and lets the start power from the ignition to get to the starter.