Okay, here's what I found. Let me know what you think. It's strange.
Tests have been done with key on only (unless otherwise instructed)

Check volts at SCR positive. Should be battery volts. If not, check power fuse:
Yes, full battery voltage.

Check volts at T2. Should be zero:
Yes, ZERO.

Check volts at R5. Should be 3-4 at creep reducing to 0.2 or less at top speed:
No! 4.8V no matter the accelerator pot position!

If R5 remains about 4 volts, check accelerator:
I checked the pot resistance at R4-R5 and it swings from 4 ohms FWD to 6K NEUTRAL to 4 ohms REV.

Check volts at R7. Should be 2-2.5 when Key switch closed:
I get 1.7V

When F or R contactor is closed and accelerator depressed, should increase to about 6.2 volts:
No change (still 1.7V)

If remains near 2 volts, check volts at lC (grey wire or 2 REC anode):
I get 8.38V

If more than 0.125 BV, check if 2 REC will gate on:
Not sure how to do that

If less than 0.125 BV, check if 1 REC will gate on:
Not sure how to do that

Check current sensor green lead to card input pin 13:
Check for what? It's there and has continuity.

Check 23 FIL for shorted resistor:
No short. 8 ohms, I believe.