Searching for 12v switched power after ditching ballast and installing aftermarket electronic ignition

Bugman said
That J3 14 BR ,suggest you test that connection for back feed. From blow up of relay inside wiring appears to not be connected to any thing else. To be sure put 12 volts on J3 and then see if voltage shows up on other relay connections

I read it the same way. Key in any position otehr than start and J3 is isolated from the other relay terminals.
Key in start, power from ignition switch through the safety switch (S2 to S4) causes the contacts to connect the battery feed to the J3 (lower contact). The upper contacts send power to the starter solenoid.