The reason your center stringer extends down into a keel, is due to the very shallow deadrise you have at the stern. It helps with tracking and tight area maneuvering.
That "crack" just looks like some delam, you should grind out that area, and add some fresh glass.
If the bulkhead with no drain you are refering to is the cabin to cockpit separation, Mine was set up from the factory with a drain hole, but it was plugged with one of those rubber flip open plugs, and kept closed. This keeps water from coming up under the cabin, from the rear bilge. The reason for the plug is incase of catastrophic conditions, like a rogue wave swamping the cockpit and filling the lower cabin, the drain allows access to let the water back out. It was the closed plug that saved my cabin structure from water intrusion and rot. Mine has a pump forward of the bulkhead, to pump out any water from the shower, or open door, hatch, ext. You can add a pump up there, and route the hose back towards the engine bilge, where you should have redundant pumps, for safety, since there is no flotation foam.
