Ok, your Captain is wrong about several things here...
1) The outer pane is not a load-bearing pane (the INNER one is) and thus is not directly influenced by Delta P.
2) If you want to decrease Delta P. on the B737 Classic, go to SBY mode ( with the non-digital pressurisation controller) and change your cabin altitude to a higher one than the standard placarded value ( given for a Delta P of 7.4psi below 28000' or 7.8psi above 28.000'). Selecting a lower flight level than your actual cruising level in auto mode will cause greater delta P, going into the yellow band above 8.0 psi I think (but this I don't recall ever doing so I might be wrong here)
3) FOLLOW THE QRH!!
