I can't really follow the detail that you added, but aside wind effect, the only forces that matter here are the weight of the person and the boat, and their correspondent lever arms. The rest cancels out.. You could also take the person out of the system you analyze and think of the rope tension as an external force, but it's worthless, the forces A, B and C that I think you are detailing (rope attached to three different positions right?) would have a different cos(anlge) but also a different magnitude, which gives the same result if the person is on the same position (except the rope has different tensions on each case).