Im no mechanic but fairly handy DIYer, fitted suspension kits and coilovers on three different cars. I personally didnt worry to much about torquing up the top mount nut, give it a light blast with impact wrench but not mega tight you may want to remove it one day. Basically because the piston spins the not will never work its way lose. not really sure about your first problem, when you say you can pull off the top mount after it has been tightened down do you just mean the rubber cone that makes contact with the shell of the car?