Hope you can understand my chicken scratch drawing. This is the simplest way without having to rebuild the structure. The blocking will keep post from moving by jamming itself against the post and do bolt the post through the rim joist. The only weak spots are the ends where it takes the blunt of the tension from the cables (if you can live with looking at a cross brace, this is the time to do that). That corners must be strong and pre-drilled with bolt and or metal holding it in place. The blocking that run along the floor joist keeps the post from moving front and aft. This isn't too important because there's no cable tension on it. At the end of the day, I favor steel posts but they don't have the warmth of wood most people like.
