I'm afraid something must have gone wrong in the checks.
It is much more difficult to check the final drive ratio by turning the tyre instead of the propshaft especially if you are not sure what sort of diff it is. It is much easier to put a mark on the propshaft and on the inside face of the tyre so that you can see it from underneath and count the propshaft turns as you can see both marks. It should be in the range of 3 to 6 propshaft revolutions for a single revolution of a wheel. Only one wheel needs to be jacked up for this.
As for the LSD, with only one wheel jacked up and the propshaft locked by putting the gearbox in "Park", can you rotate the wheel that is off the ground by hand in a forward direction ? With an LSD, it should move but be very stiff. If you cannot move it by hand then it is either a badly set up LSD ie locked or a non LSD.
Doug