RE: Pilot hole too big
Well its no big deal.....after all when you're finished you're goinng to have a 3 mm hole. I assume you're using wood screws not machine screws. go ahead and torque in the screws. I didn't say over torque in the screws. now if you're still worried about the screw holes remove the screws and drop in a couple of drops of thin ca glue and let dry. This will reinforce the threads cut by the screws.
Or step up the screws 1 size, or drill all the way through get longer screws and secure with a blind nut or lock nut. Kinda hard to tell whats what without a pic...
good luck