I want to add a hot water recirc line to my trailer

First Question: when I am boondocking, that water faucet isn't always nearby.

Second Question: by opening the tee'd valve on the hot water line, it is no different than using the hot water in the shower, only the cold water in the hot water line is being evacuated into the cold water tank. I would leave the valve open for maybe 20 seconds so the hot water has a chance to refill the line up to the tee, and then I would turn it off.