After some help from @mc-hamster and digging through the files in VS Code, I noticed that there is the option of an external button for the middle button only already in the code.
Putting a button between GPIO 13 and GND mimics the middle button. EDIT: Accidently found out that the pin labeled RST, is obviously for wiring a reset button as well.
For the power button, my original idea should still work, but isn’t really ideal.
I only want a middle button externally mounted, as I don’t want there to be a chance of being bumped and powered off. But I will continue to pursue the other two!
Pretty happy with my set-up so far! Three 18650s batteries, upgraded GPS. Just waiting for my external button, and going to relocate the screen to the right orientation and adhered to the clear lid.
Also waiting for a rework station to repair my t-beam that I fried a chip on with my antenna cable shorting out to the positive battery terminal while wrecklessly assembling.
I havent fixed it yet, but after playing with a Dewalt heat gun and bending some pipe to slip over the end, I realised it might be time to invest in a new solder station. Especially since my Samsung TV has now started giving me grief. I might have to replace 3 chips on the mainboard.