Yes, you have unscrew that yoke several turns and that will solve your problem. That yoke should have never been tighten against the base. It should always be free to turn. The snap ring is used just for the user not to unscrew it too far by accident.
Personally, I normally remove the snap ring and don't put it back on. I just pay attention not to unscrew it too far.
Do not think about modifying the yoke! That ridge is part of the yoke. They all have it. That yoke will fit every valve you will encounter when it is free to turn.
Someone tighten the yoke too much and some corrosion is probably affecting is keeping it from turning. If you don't have the proper tools to loosen the yoke, then send it to Bryan for service. That regulator could probably use some service anyway.
I am a very strong believer on; "if it ain't broke don't fix it", but that first stage does look like it could use some service.
Buceador con escafandra autónoma clásica.