How does the actual acceleration compare with the theoretical acceleration?

You forgot to include something in your question, so it can't be answered.

To find the theoretical acceleration, you must use the following formula: Acceleration Theory = Applied Net Force / Total Mass Applied Net force (F): F=Ma

Acceleration is the rate of change of velocity aka how fast the velocity changes

Yes, acceleration can be positive and negative because acceleration is a vector. It has both direction and magnitude. The direction is what makes it positive or negative. Negative acceleration is...

In the rotating frame, it can be (though it doesn't have to be). In a non-rotating frame, no (though it can be uniform in magnitude).