First, there is no restriction against bringing your own food on Amtrak. None whatsoever. You can't ask the Amtrak staff to refrigerate or heat it for you (health regulations), but you can bring it. Coolers are valid as carry-on luggage if they otherwise meet the size and weight restrictions. You have to eat your own food at your seat or, on trains with Sightseer lounges, in the upper level (non-cafe area) tables of the lounge car. And while food is allowed, carry-on alcoholic beverages may only be consumed in private sleepers.
It does sound as though the crew on #11 was remiss; I would call Amtrak, ask for Customer Relations, and complain. They might give you a bit of compensation. That said, you do have a couple of options. First, once you realize you've been missed, go to the diner and ask the LSA if there are any open slots left. If there aren't, ask to be put on the stand-by waiting list...sometimes folks fail to respond to their call for dinner. Finally, just before the dining car closes they normally make a "last call"...often you can get in then without a reservation. Of course, if you're dealing with an unprofessional or burned-out crew that may not help. In which case Amtrak needs to know about the problem or nothing will ever be done about it.
Finally, remember that the crews work both ways...not on the same day, of course. That lazy crew will be on #14 going north once they've had their rest period, and your good crew will be working #11. So place the blame on the specific crew, where it belongs, and not on the train (or Amtrak) as a whole.