From the novelization, they suggest that the Jenolan was transporting cargo and a bunch of passengers, including Scott. During the crash, the passenger compartment was torn open and everyone there was killed, and something similar happened on the bridge, killing the rest of the crew. Scotty was in Engineering with Ensign Franklin, which was not as damaged, allowing those two to survive.
Back to the Ambassador, we know they HAVE torpedo bays from dialogue in "Yesterday's Enterprise", though the model has never been seen firing anything of the sort (sorry Timo, in "Emissary" only phaser fire was seen from any ship, though dialogue similary supports the Saratoga having torpedoes). I like the idea of torpedo tubes that are simply hidden behind slideaway doors for whatever reason... And in terms of the lack of phaser coverage aft, if the existing phasers keave blind spot I see no reason they can't have tiny point phaser emitters a la Lakota or Defiant. If the Ambassador was really a pathfinder kind of ship, I see no reason why they can't have a mix of weapons technologies in the design, even as a redundancy in case the fancy new phaser strips don't work out well.