When we level the Newell Coach we argue about "level" We come very close Often exact center is impossible - we get just a hair off the center. How far off the level mark is dangerous for the fridge. I consider any thing within most of the center on the level to be acceptable.
RV fridge mfg. states: Norcold's Leveling
Comfortable vehicle leveling is well within the refrigerator’s operating requirements of 3 degrees off level side-to-side and 6 degrees off level front-to-back (looking at the front of the refrigerator). Continued operation outside of these limits can result
in irreparable damage to the cooling system.
To ensure proper leveling with these models, the vehicle needs to be leveled so it is comfortable to live in. (No noticeable sloping of floor or walls).
In other words...if the RV is level enough to be comfortable using it then it's level enough for fridge operation.
When the vehicle is moving, leveling is not critical as the rolling and pitching movement of the vehicle will pass to either side of level, keeping the refrigerant from accumulating in the piping.
In the end How 'level' is comfortable for your wife?