I use the levels supplied with the leveling system...seems to be close enough and I prefer the left side to be very slightly low and the front very slightly high. Fridge doesn't seem to care if it's perfectly level or not so I abide by Dometics instructions:
"The vehicle needs to be
leveled only so it is comfortable to live in (no noticeable
sloping of floor or walls)."
Works for me, no sense obsessing about level and I can get my after traveling cocktail quicker.