congrats on progress sorting out issues.
sorry I can't answer all the questions you have.....possibly tackle one at a time, completely understand the highs and lows with owning a pinball machine.
not a criticism, but the EOS switch is not a proper one with tungsten tipped contacts to allow for the extra current.
it's a shame sellers don't sell the correct product, maybe notify them that it isn't correct and has standard low voltage switch contacts? Assuming they are obviously unaware of the switch stack being wrong for a correct EOS switch stack?
assuming you have that black rubber piece added to help open the EOS switch? This is not needed but a tweak of the contacts to open them to about 3.2mm/ 1 /8 on opening on full travel/pull in of the plunger.
again not a criticism, just an observation, but the unshielded section of the red wire isn't idea, and there appears to be a strand of the wire very close to the other EOS solder tab which if it connects will cause problems.