It should be OK. Just a learning experience! Plus an opportunity to improve your guitar building skills.

"Would it be a strong enough bond to drill the machine head screw hole a bit bigger, wax the screw and re-fit it?"

It should be fine (and possibly the strongest part of the headstock). I would get the glue in the gap while the screw is still in place (as it will keep the gap larger), then remove the screw, then clamp it.

The tuner hole may need to be redrilled after. I would possibly try a slightly (real slightly - maybe sanded/filed) bigger hole for the bushing (I feel the bushing contributed to the crack), and add a few drops of CA glue to keep it in place if it is a bit loose (the CA could also to strengthen the fault line).

Others may suggest different options.