Im wondering if you are missing a power feed from the ignition switch which is just a set of SPST switches - perhaps one is bad. You could do a switch bypass test for the cost of a few inches of 18AWG wire.
I installed brand new battery for staters then started check things again with the power probe.
I have an OBD2 scanner (actually a few), there is power to the OBD2 connector but the scanner (all 3) is unable to make a connection with the ecu?!, just like the dash? It has to be the same wire/wires. On the OBD2 port itself I get resistance on pins 2, 10, 13, ground on pins 4 & 5 , power on 16, but nothing from pin 7? (it's a white wire)
So after studying wire diagrams OBD2 Dash Harness & PCM & what they have in common by chance I came across on two different diagrams that they also all shared a white wire with the O2 sensors, back to the original problem my upstream O2 sensor melted on the exhaust manifold & grounded out, I replaced the O2 sensor pigtail then traced some wires to the battery junction box, I had checked ever fuse more than once. (I also got new glasses yesterday) So I busted out my voltmeter placed it on resistance & started to check a select few fuses the I wrote down #1 Maxi fuse good, #8 good, #9 gooo… wait a second not good!? Upon closer inspection I found the short! I had to take a pic with my phone then enlarge it to see it clearly, but it was probably bad the hole time probably from the O2 sensor grounding on the exhaust. I had looked at it, but didn't see it, I guess all those scratches on my old glasses didn't let me see as clearly as I thought. I swapped the 20 amp Maxi fuse out with fuse from parts car, dash lit up, OBD2 scanner started working, & it started right up!! I still need to replace the upstream O2 sensor itself, but it runs!