Amtrak can still turn tables 3 times. And the food on amtrak traditional dining cars can be outstanding as well. I have no complaints about the current amtrak traditional dining car menus. (Though if they brought back the Mahi Mahi, Lamb Shank, and Crab cakes I wouldn't complain!
"Lowering the red ink" gets a bit tricky because adding staff adds considerable expenses that wouldn't be paid by a few more coach meals. The best way to lower red ink is to use the existing staff more effectively. This means
1 - offering room service so sleeping car passengers know it is available - the more sleeping car passengers choose room service the more room for coach passengers to pay and eat in the diner.
2- offering at-seat meals from the dining car delivered to coach passengers.
After 1 & 2 if Coach passengers are still being turned away from the dining car, consider adding dining car staff to accommodate them but with the current train consists I don't think that would be the case.