The Southwest $134 fare is refundable so what are you waiting for? Buy it and watch/monitor for a cheaper fare.

The AmericaWest $92 fare is their "red-eye" flight leaving at midnight. It is non-stop but you'll get to SFO at nearly 1:30am.

You might try Sidestep.com. Sometimes when Southwest's site shows unavailable on certain flights, I was able to link from Sidestep and purchase a ticket.

I think your $134 fare is not bad for Monday. Fares are cheaper Tuesday-Thursday and I don't think you can count on earning NW miles for this itinerary unless you are willing to pay more for your tix.

Good luck.