Another check…
Put the bike into the center stand and then place it into 6th gear. With some moderate force you should be able to rotate the wheel. If the wheel won’t move, you may have a stuck engine.
Has this bike been outside all winter?
Not a lot. Disconnect the connector at the brake switch. Attach your tester to the two prongs, apply the brake and listen for the magic continuity beep. No beep…then you have found the problem. If it beeps, you’ll have to start digging further.
I have replaced a number of brake light switches over the years (never on an FZ) so they do fail. It is possible that they both have failed. A continuity tester is your friend here.
I'm sure I understand what you mean by "By using code 30 I was able to have it reliably produce a spark"
Fault Code 30 is the lean angle cutoff switch. This would produce the exact issue you are experiencing. You didn't mention that the bike had fallen over...has it? It is possible that the...