I’ll try to answer your questions:
1. Dinner reservations did exist, but not on most trains. I remember very well standing in the corridor along the kitchen for seats in the diner. The diner did not differentiate between sleeper and coach passengers. Since the diners were operated by the railroad and sleepers frequently operated by Pullman, the railroad had an interest in selling as many meals as possible, and no interest in discriminating against coach passengers. There were some trains that were all Pullman, or that had coach and Pullman sections with separate dining cars. Santa Fe’s Super Chief and El Capitan which usually ran combined, is an example.
2. Open section Pullman accommodations, which were considered “standard” were open with seats facing each other, that folded into separate lower and upper berths (not called bunks). The US never had three berths stacked except for an experimental car in the early post war, and in troop sleepers. The European couchette usually has three berths on each side of the compartment. There were many private room Pullman accommodations, none with three berths stacked. The most common were the roomette, bedroom, compartment and drawing room. Variations included the duplex roomette, master room, and later, the Slumbercoach which was essentially a spartan duplex roomette with a narrower bed and sold for the price of a coach ticket with a space charge. In railroad days, there was the rail fare, the Pullman fare which was more, plus the space charge. The more fancy the accommodation, the more the space charge. In addition, a minimum number of base fares were required to occupy a larger room.
