If all you want is "a little 3D" then you're probably OK, but the elevator and aileron areas are definitely on the small side for 3D. This model was designed for sport/aerobatics, not 3D. If you want to fly it entirely within its design envelope, use moderate throws on elevators and ailerons--15˚ or less. Rudder throw should be as much as can fit between the elevator cut-outs. If you want to push the 3D limits then you'll need more throw and more torque on elevators and ailerons, more expensive servos... probably not money well spent in this case (although you could use them in future models to better effect). If you want 3D, you should set your TX up for dual rates. Skip the 3D part and stick with single rates for a more foolproof setup.

As to CG, I would go straight for 30% of mean aerodynamic chord. The wing is slightly swept back, but I think you can safely take root chord + tip chord, add them up, divide by two, and use that for your MAC. Root chord maybe 15", tip maybe 9", average 12" for MAC. 30% of 12" ~ 3-5/8", which would be a good starting point. So find the part of the wing that measures 9" chord, and on that chordline go back 3-5/8" from leading edge, then run a length of tape back to wing root from that point, perpendicular to fuselage, and balance on that line.

Two cycle 1.20 would be adequate power, 1.40 would be better, 1.60 would be about as far as I'd push it. If I were buying a new engine for this model, I'd go for a SuperTigre 1.40 (G2300)--good power, reasonable cost, reliable runner.