If you don't use loktite on the grub screw, it'll come loose eventually. Y don't want that to happen. And btw, did you use loktite on the motor mount screws? If not, do it. The incremental increase in power has nothing to do with proper setting of mesh. Use the paper method to set your mesh. Proper is proper. If you set it too tight, you'll ruin your motor bearings.
The whine you hear may be the motor bearings complaining, because you have the mesh too tight, or it could just be the sound of the new motor. I would have had to hear the original setup to be 200% sure. But it sounds fairly normal to me.