setting dwell angle on a m115 w123

need to change the contact breaker point on a m115 but don't have easy access to a meter so want to try to adjust it the "manual" dwell gap way.

despite putting it in gear and trying to move the car, i can't get the cam to move to the "high point" to adjust the point gap. (no i didn't forget to let down the parking brake)

how is the engine supposed to behave if the gap is too wide, and when the gap is too narrow?

many thanks in advance.