I thought maybe I saw your problem so here goes. The 25 in\lb has nothing to do with how tight the pinion nut is. It is the amount of drag required to turn the pinion and carrier. So, the process. You usually have to have a fixture to fit on the pinion yoke as you are going to have to stop it from turning with a lot of torque. Fixture on, tighten the pinion nut to lets say 100 ft\lb. take the fixture off and then use the in\lb torque wrench and spin the pinion. See what the reading is to make it spin around. ( I must add there should be no axles in the side gears at this point)
If is is below 25 in\lb, put the fixture back on and turn the pinion nut a little more, ( you might be up to 150 ft\lb by now) take it all off and check with the in\lb for what torque to spin the pinion nut. Now keep doing this until the torque to spin it is 25 in\lb. At that time the pinion nut is correct. ( probably took 200 ft\lb to get to this point) If this still doesn't make sense, just say so and we will keep doing it until you understand the process.