It sounds as though the control horns on the ailerons are not lined up properly with the hinge line of the aileron/wing and also your control horns on the servos may not be set in the same place.

Not amount of radio mixing with correct this as you will change the full rate throws as well as the neutral points.

In all your geometry is not correct

On the radio, get all your sub-trims back to zero percent, get the flaperons settings (aileron/flap) percentages back to 100% and center any aileron trim you may have in it.

Now turn the plane and TX on and wait for the aileron sevos to center. Make sure the servo arms are 90 degrees to the servo body. Now, from the side, take a look at the holes on the aileron control horns and make sure they line up with the hinge line. If not move them until they do. Once that is done, connect the control rods and adjust the clevis until the ailerons are properly centered.

Your throws should not be fairly equal. Proper geometery is very important.