The original design is functionally flawed. Fortifications are about layers of defense. The corner tower should be 3 stories with a single internal access point - probably on the second floor. The next layer of defense would be the two-storey building with 'living quarters' in one wing and a barn/stable in the other wing.
The outermost layer of defense is the courtyard and one-storey outer wall.

Stone buildings are heavy, so the coast should be rocky (or a single rock outcropping) rather than some soft sand or mud coastline.