To clarify a little about pressure. Total pressure is static pressure plus velocity pressure. Velocity pressure acts in the direction of velocity while static pressure acts in all directions. A pitot tube measures total pressure at the tip (pointed into the air stream) and subtracts static pressure at right angles to velocity (through the little holes around the perimeter of the tube) to give you a reading of velocity pressure which is then allows calculation of velocity. That is assuming you connect both hoses to a manometer. If you increase velocity as in a venturi, there is a reduction in static pressure as it converts to velocity pressure where the velocity is higher (at the restriction). Reducing velocity, the pressure is reconverted to static pressure with some efficiency loss.

In a sail, increasing the velocity on lee side reduces the static pressure on that side compared to the static on the windward. That results in a force or lift which is the difference in the static pressures. I would believe there are other forces involved as well such as a portion of the velocity pressure on the windward side.

Howard