When you mount the servo's arm...You'll notice it's not going straight, straight anyway.
Use two pairs of pliers and bend it a little and just large the holes.
Yeap, hold the drill more stright the next time u drill the ailerons.
Don't worry it dosn't have to be straight, straight. becuase the servo's arm won't mount stright to being with.
That's what the threads on the cleves and the rods are for.
Btw, some elavators , you use a rod piece to joint them. They're harder to fix after you glue.

if you a havn't glued..switch the airlerons for left wing to right wing..and redrill.
or just bend the rods to compensate



well, for you second question. Sometimes it's not suppose to be straight.
Depending on the model. It's call a wash out or wash in.

you can try to warp it back with the covering, when you cover.

Even if you did have straight and true, you might wrap it when you cover.