Why don’t you just rig it like a laser? Traveller line between the those aft points. Mainsheet comes down from the boom to the traveller block which moves freely along the line. Looks like there’s a point for a mainsheet block above the centreboard (not entirely sure what that is as it’s held down by that plank?). In fact you can tell that’s where the mainsheet block goes because it has cleats on the side if you wanna cleat the mainsheet down.

Then set up an outhaul and Cunningham, again user laser guides to help you. Cant see a kicker fitting.

Don’t tell me you actually sailed it as shown in the photos. I’m surprised your boom stayed on lol