During your attempt to hover, it will be item number 3 the Slipstream Effect, also known as Corkscrew Effect that is the biggest culprit.

The engine power is very high and the airflow or forward progress of your airplane is nearly non existent. The Corkscrew Effect is VERY pronounced and can be visualized as very tight threads like a screw twisting around the fuselage. Therefore the twisting slipstream does push hard on the rudder from the left side (for American engines that turn clockwise) and therefore the need for the pilot to hold a significant amount of right rudder during the maneuver.

Much of that can be adjusted by fixing right engine thrust. One would probably not put enough right thrust to totally remove the need for some application of right rudder. Most full scale aircraft designer’s attempt having just enough right thrust for the most common flight regime, which is level flight. During climbs and descents the pilot must make the adjustment. That is, hold right rudder during climb and left rudder during descent.

It is also significant that a large amount of air will sneak through the hinge line and rudder authority can be significantly reduced unless the builder applies gap sealing to the hinge line. Simply applying gap seals can effectively be the same as a 20 per cent boost in rudder authority.

By the way, Slipstream or Corkscrew Effect is the predominate torque problem for airplanes and as long as the prop is turning (or not) it is an issue. The other three pales in comparison, and exist briefly during certain phases of flight

The student who did the initial explanation is to be congratulated for learning his lessons well. Good luck in your hover practice ---
Hope this helps.

CFII - Single and Multi Engine Land