duffieldde Is this limitless timer a GrapheneOS feature?
I believe this is how the hardware works.
duffieldde How long must I leave the phone untouched before the single attempt it gives me goes away and I am able to make several consecutive PIN attempts again?
I believe it is necessary to successfully unlock the device before it will reset to normal behavior.
duffieldde Why is the PIN I always use not working to unlock the phone after I wait for the phone to allow me to make another unlock attempt?
If you have entered the same PIN 130 times, probably entering that one in again isn't going to work. But if you are sure there is nothing else you could enter, I would recommend writing it down on a piece of paper and then asking somebody to enter it for you.
duffieldde What could have happened? Why is the PIN I always use not working to unlock the phone after I wait for the phone to allow me to make another unlock attempt?
In theory the secure element (which is hardware) might have failed. This is genuinely quite unlikely, but in theory it can happen, just as any piece of hardware can fail.