Are you pre-drilling for the screw holes? I think the fact that you
need an impact driver tells me something's wrong. A properly
pre-drilled hole should make it easy to install and remove the screw,
without compromising strength (and might be stronger).

I've also started using McFeely's screws (or other "real" screws) where
strength counts, I've broken many a box-store screw, but the McFeely's
screws will destroy a piece of oak (or stall my big hammer drill) before
they break.

(And yes, wax is good. Never use soap on a screw.)