You said you were going to study the diagrams, and hopefully your steering column work will fix the problem. In case you still have to do more troubleshooting, you are correct, the brown is for the running lights ONLY. The green wire is the brake light AND the turn light.
If you look at the diagrams, that is why the turnsignal switch looks so complex. When the lever is in the center, it directs the brake switch signal through to both rear taillights. When the lever is moved right or left, it lifts that certain bulb off the brake circuit, and puts it on the blinker circuit. The brake circuit and the turn circuits use the same wiring to the rear and the same bulb filaments in the rear.
