Mesa 7i73 IO Questions

I'm making some break out boards for my 7i73 and I want to verify my understanding of the IO.

There is the Key Matrix, that part is clear enough to me.

then we have Inputs. 8 - 15 being 5V tolerant and need to have buttons wired such that they pull the input to ground when pressed?
Inputs 0 - 7 are only rated to 3.3V and are not pulled up or down. so I would pull them up to 3.3v before using for a button.
but I'm completely confused by the analog reference voltage pins AVDD what do they connect to? it's mentioned in the manual that they are for "ratiometric measurement applications (like potentiometers)." but my google ability has not given me any idea how I'm meant to deal with those 2 pins.

then the Outputs if I'm understanding correctly OD0 and OD1 can be used in place of OUT0 and OUT1 as sinking outputs otherwise everything else is a sourcing output? that is providing 3.3v up to 4mA?

thanks.

An example of AVDD usage would be a potentiometer:
One end of the potentiometer would connect to AVDD and the other to ground
(with the wiper connected to an analog input)

OUT1 and OUT2 are 3.3V push pull outputs (so 4 mA source or sink)
OD0 and OD1 are high power sinking outputs driven by OUT0 and OUT1

Thanks, that clears up my uncertainty.