Oops, not watched my video. You're description up there ^^^ is contrary to the Merc manual, and my experience. You adjust for the correct engagement of FWD first (with the cable barrel) and then do not move it again! Then adjust the shift lever anchor point in the slot for REV engagement. No other way will work properly.
I'm aware you designed and manufactured drive trains for a living, but this is an area I have done a lot of research and study on. Any deviation from the Merc prescribed procedure, as outlined in my video, will result in the operation of the shift system being unsatisfactory. And yes, that is my experience, having been doing this and adjusting these cables, and fixing up other people's mess-ups, for more than 30 years....
Chris.....