What do you mean by “not floating”? Are you unsatisfied with the speed of gravity?
Note that blender’s gravity (which can be changed in the Worldbuttons) is in relation to Blender Units (BU). The default value for gravity is 9.8 BU/S^2 (9.8 blender units per second squared). This is an acceleration of 9.8 BUs. 9.8m/s^2 are the units of “real life.” The equivalent in feet/second is 16 ft/s^2. Make sure that your characters are to-scale (ie, a character should be about 2 BUs to fall at a correct speed).
The reason you have to add more power to move your character is because of friction. You have to work harder to go against friction when the force pushing an object into another object is bigger. Just think of lightly skimming your hand along sandpaper, and then putting all of your weight onto the hand and moving it along the sandpaper then.
To solve your servo problem, select each axis (X, Y, AND Z) instead of just one of them, and set the corresponding linV values to something really small (like .01). This will stop your “it’s not dropping anymore” problem.
Hope that helps!