misalignment
take a pin and stick it into top center of the front of fusalage, like on top of the firewall would be good.
attach a length of string long enough to reach the trailing edge (outer most tip) of the horizonal stabilizer.
mark the string with a dark marker,then check the opposite side to see if it is the same.

If it is then it is fine, and the wing is off center.
do the same on the wing with the attachement bolt or bolts in place
if the mark you make on the string at the trailing outermost wing tip on one side is different than the other, remove bolt and
adjust wing until you get the same measurement on both sides.
to fix the misalignment you may have to add to, or make a new attachment bracket.
dont forget to make a mark on the wing once it is centered.

the only way i know to fix the horizonal stab if it is off, would be to cut the hinges remove the elevator/halves and square the trailing edge of the stab. then make new hinge locations between the old ones, and reattach the elevator.
dont alter the elevator. it will be straight once the trailing edge of the stab is straight

the stab fix would be a lot of work, id wait and see first how well the plane will trim before making that dramatic fix.

center of gravity
for that type of plane a little nose heavy may not be critical, a plane is easier to fly nose heavy than it is if its tail heavy.
if after adding a little weight it is still very nose heavy, buy a wire extension and mount your battery as far back in the tail as possible.
you could remove the covering over a lightening hole and mount the battery to a bulkhead. run wire to receiver and recover the hole.

let us know how its going[8D]