You're mixing up your directions. Say a person is spinning in a cylinder.The centripetal force is the push on his back of the wall of the cylinder which keeps him moving in a circle, instead of flying off on a straight line. Try twirling a rock around on a string, and then let go (make sure no one is near by to get hit!). See - it will fly off in a straight line. The string provided the centripetal force to keep it spinning, until you let go. This is the viewpoint of the INERTIAL observer - someone who is on the outside, that is in this case, you, watching the rock on the string.

Now, CentriFUGAL force is what you FEEL when you are inside the cylinder, and you feel like you are being pushed out.

Centrifugal force is not a"real" force in the sense that you only feel it when you are on aNONinertial platform, like the spinning cylinder, or a car that is accelerating around a curve. When you go around a curve in a car, and you feel pushed sideways - that is centrifugal force. It is your body's natural reaction to the centripetal force, which always points in towards the center of the circle.

So - the spinning cylinder creating artificial gravity: the artificial gravity will point outward. You will walk on the walls, but you will"think" the walls are the floor. Suppose you create a spinning space station spinning at a rate such that the rooms on the outside perimeter are maintained at 1g. The closer to the center you get, the less artificial gravity you have. So, put your zero-g testing lab at the very center!

I'm not sure what you mean by a "hight-mass sphere. "What you're describing is basically being in orbit, where gravity is providing the centripetal force (or acceleration).

Check out the Wikipedia web page for gravitational time dilation: G time-dilation which has these three cases (orbit, hollow sphere, solid sphere). You can't cancel the forces; they all add up, and time always goes slower for you.