Yo! I did read through and have been trying to reply but bots or mods are blocking me. Ground the bottom REAR blade to rule out that the neutral safety switch isn't grounding that. (make sure you are in park or neutral) It's the front MIDDLE blade that goes to the solenoid. Two things there: One, that, energized should make it crank WHEN the lower of the three gets juice from the ignition switch, ironically powered by one of the fusible links off the big post on that same relay.
So guess what, I have company. Try grounding that bottom rear and turn the key. Also put a meter or light on the middle one and see that the switch is juicing it, and see that jucing the wire off the bottom blade makes it crank.