As long as the diameter of the Watts is similar to the AquaCity so it will fit in the holder, it isn't too long, and the adaptive fittings will work, I don't see why not. Note that one reviewer found the same unit at Home Depot (3 years ago) for a little less money. I think though that I recall finding "generics" for the AquaCity model that were even less. Remember this is an ice maker; it doesn't pump very much gallonage through. The larger unit may be overkill. If you do order through Amazon, be sure to enter through the Amazon portal off the BAC Home page (the link isn't on this Forum), so the club will get credit from Amazon.
As to the pressure gauge, I don't have one so will defer to others on that. If its on what appears to be the city line inbound, I don't know why it would read 80 if you have a 50 lb. limiter at the park faucet. From what I've read here, 65 psi is about as much as you should ever allow a regulator to stress the system components with.
By the way, you should unscrew that mesh pump filter (between the pump and the white elbow) and check the screen. If it's been awhile, it could have calcium buildup or just need cleaning to allow optimum pump performance.
Joel