Nose pulls up with the application of power= too much engine up thrust. Nose dropping when power reduced implies the same. Since you had control power off I would be using an incident meter to establish just what the thrust angles actually are.

Elevator trim can cause a lot of issues if overlooked. First flights can be a lot easier when a little nose heavy. Never, ever, trust an instruction manual to be correct with either CG or control throws. Each is an individual performance preference item with some manuals being close while others are not even in the ballpark. The safest flights will always be nose heavy. Not generally the best performing but safest for establishing a starting point. Establish CG fine tuning after the first couple of flights, using trim offsets as a general guide.