Taking your questions one at a time

It tends to want to lose altitude during an turn.
this is normal, as you turn you tilt the wings which causes the plane to side slip slightly and loose altitude, you can try feeding in some oposite rudder to maintain the same height.

Requires some down ailerons to maintain level flight
Down ailerons??????? i asume you mean down elevator, what throttle setting? have you adjusted the trim on the control.

Flys at half throttle level, full throttle wants to climb.
if its a flat botom wing some climbing as the speed increases is normal, if its excesive try shimmng the TE of the wing up or give the engine some down thrust.

Would moving the CG forward some improve any of these traits?
possibly help with the climbing under power but i'm not sure, normaly a rearward CG makes the plane realy twitchy whatever the throttle setting.

heres whar i would try,
forget loosing altitude during turns, thats normal.

add some weight ot the front so cg is where it should be, if thats no good shim the TE up

try these first as there easyest.