The schedule described to you was fairly accurate; most pilots do fly out early, lay over, and come back in the evening. It's just the nature of the job- the customers need their stuff as early as possible, and it comes back after the close of business. If you were watching the Metro during peak season that might explain the roundtripping. Otherwise, most pilots leave between 5 and 7AM and come back between 5 and 9PM, with differences between the bases.

A PA31 slot in OAK would pretty much be a lock if you asked for it. As for hours, it's likely you can average three to five hours a day. I'm not sure of the reason for the sudden increase in hiring, but as long as the market doesn't drop much more I figure stuff will stay fairly steady, so it's a decent time to get hired.
My feeling is that air freight is a little inelastic- a lot of companies need what they need and cost is secondary. As long as customers want to offer next-day air to a destination, they need a feeder, so even if volumes drop off we're still flying the routes.