I wasn't suggesting that what you have done hasn't worked Dottie, clearly it has, I'm only questioning the reasoning behind why it has worked, and what was the initial trigger.
Certainly as David pointed out, once there has been and episode, the start of a "bout", that in itself will have weakened the sphincter, and treatment is needed to reduce the acid levels to let the sphincter recover... that is why, after recovery that may be aided by a dietary change, you can often go back to the original diet. if that is the case then the change in diet may have aided recovery, but it would seem unlikely that the original diet was the trigger, at least not on its own.
I also notice that you now soak the kibble and serve in four meals, both of those coula also be part of the reason the diet change has helped... soaking will add more water, to help dilute the acid, and the reduced portion in each meal will allow the body to process smaller amonts, and so the tummy will be less full at each meal, leaving more room and so less chance of excess acid coming back up.
What you have don has worked, and that is a fantastic result, but as I said the cause or solution is likely to be far more complex than simply changing protein percentage, and that in itself could be masking the real cause/cure.