Your post contains the solution. You said that the “cg is nose heavy". The forward cg makes the airplane very stable in pitch so that any increase in speed produces a drastic pitch up. Move the cg aft a little at a time until it flies like you want it to. As you approach neutral stability (rear cg limit) it will just go where it’s pointed with little pitch change at any speed. Just ahead of the this neutral point is where aerobatic pilots like, but depending on your experience level, you may want to keep a little greater stability for ease of flying. If you want it to fly well inverted, take out the down thrust and mount the engine level. You won’t need the down thrust when you get the cg right.

With a flat bottom wing, the stabilizer should be set at zero incidence, as well as the wing.