Chasin Tail, Being a "hip holster" guy, I can't help you with a shoulder holster but I can give you some guidance for your loading gate, which is a very common issue with all New Model Ruger SAs..
Ruger uses an odd shaped flat spring for the loading gate where the tip of the spring rides on the loading gate's pivot pin. As you open the loading gate, the tip will find a flat spot on the pivot pin and detent to the gate to the open position. When you go to close the gate, again the tip of the spring will bind on the "flat spot" until it is almost closed, then will detent to the closed position. The problem is .... when the tip of the spring is ground to shape at the factory, it often leaves machine marks in the tip which creates a lot of friction between the spring and the pivot pin.
Try this: remove your cylinder then look at the inside bottom of the loading gate to find the loading gate spring tip and flat spot. Force some heavy grease in this area then operate the loading gate multiple times to get the grease under the loading gate spring tip. This should free it up where it works smoothly. If the spring tip is really rough, you may have to totally disassemble the gun and buff the loading gate spring tip until it is nice and smooth. Generally, the grease trick works well and after some use, it will eventually smooth out work with little effort.