Another starting circuit question

[JMBT]

Thanks for all the great ideas guys.

JimT: no I have not load tested each battery yet, I will do that.

Snailexpress: I got rid of the master battery disconnect a few years back when it failed.

Baco74: I am not familiar with the solenoid on the firewall. Inside under dash or outside?

Nilao: are you talking about the large one zip tied to the main wire harness by the ECM?
Or is there another one? I pulled that one cleaned all the terminals and socket., also tested it for high resistance and continuity in both positions.

Marek4792: No, I only have to turn the key one time. Are you talking about the relay outside near the ECM or a different one?