I've fixed a number of necks, including a Gibson Les Paul Studio with a broken headstock. From my doctor, I got a syringe with a needle of about 1/16th and matched it with a same sized drill. I drilled a number of holes around the crack, then applied tension to hold the crack slightly open. Fill the syringe with tightbond, and inject into the holes just till you start to see it come from the crack. Then close up the crack and clamp, wipe up excess, wait two days and string it up. It's questionable how much this will affect the truss rod, if it even has one. Either way in the end, if it doesn't work out, I would look for a 30" replacement, which would be much easier to find.