Pray tell, any info on what F38 was supposed to address? Can't say I've heard mention of that one, and for that matter didn't receive any notification of it from Chrysler either.
Increased fuel mileage could be due to the engine getting broken in with more miles (common with diesels) and high quality fuel. After my experience with Chrysler TSB's and recalls, I'm highly skeptical of them doing ANY reflash to actually make this beast perform better.
Echo the sentiments on venting/bleeding the fuel filter. Had the same experience when I still had the stock fuel setup. Keeping all the air bled out of the fuel filter made the problem go away, and when it would reoccur I knew it was time to vent the filter again.
Also, fuel filter is supposed to be changed every 24K miles per the owners manual at minimum - some (myself included) change theirs out every year just before winter to preclude any cold weather problems.
Check your fuel heater electrical connection on the fuel filter as well - after you've vented the filter to eliminate all air, unplug the connection and operate the primer pump to pressurize the filter - then look inside the connector on the filter to see if there's any diesel fuel weeping out. If so, that leak will allow air to be sucked into the fuel system when operating, and diesel fuel in that connector can also present a fire hazard when the heater is operating. There is an upgraded version of the fuel filter assembly available from Chrysler if it needs replacing.
There has been a TSB out for at least the past two years addressing the problem of the battery being drained dead after a few days, involving a reflash of the appropriate module. Tell the dealer to check thru the TSB's - sounds as if he doesn't know of it.
Timing belt changeout is listed in the maintenance schedule that came with the owners manual - around 80K to 100K miles if memory serves.