I'll take a stab at #1-3.
The observation car (obviously) ran vestibule forward. However, 22 roomette cars were rare on the century. I can't find any indications of this car line in timetables until combination with the Commodore Vanderbilt in 1958. At that date, I believe that the Budd-built HARBOR series were more common. The 4-4-2s, 10-6s, 12 bedroom and (I believe the) 22 roomette cars cars all ran vestibule to the rear; although, on occasion, you might see one of the 4-4-2s or 12 bedroom cars vestibule forward. (I only have a diagram of the BUDD-built HARBOR 22 roomette cars, which had a rear vestibule; so, I believe that the BAY cars were similar.) The intention was to point the higher priced accomodations toward the Hudson river for NYGCT departures; operating considerations sometimes took precedence. Where roomettes were present, the intention was that the occupant ride facing forward, which is why the bedrooms are located on the "wrong" side of all NYC 10-6s.
The dining car would operate with the dining room forward, and the kitchen dormitory to the rear (vestibule to the rear). You must place the kitchen end of the KD adjacent to the cabinet space of the dining car, not the waiting area. (The waiting area had windows close to the car end; the cabinet end had no windows. Look at the car ... you'll figure that one out.) The mid-train SHORE lounge car ran adjacent to the dining room. I believe that the SHORE car was intended to run vestibule forward, since there was a general lavatory at the other end of the car, and they wanted this adjacent to the dining room.
As to #4, I believe that shlustig was correct, with a possible exception. The whole train was turned at the end points. But, I believe that the RPO was removed, sent to the adjacent postal track, and returned to the departing consist without being turned. I've seen pictures with this car pointing either way. Mostly, though, the pictures show the car operating (looking like) 1 door/windows/2 doors.
Hope this helps. And, BTW, a complete consist should have at least 3 10-6s, 3-4 12 bedroom cars, and 3 4-4-2s. And, you should (probably) have 2 SANTA FE sleepers (a 10-6 PINE-series and a 4-4-2) behind the RPO.