Well, I think I figured out the solution for the hot water line and the check valve on the water heater.
Lowe's carries all the parts I would need to replace that check valve including the valve itself, and create a disconnect at the same time.
The disconnect would be two push-fit Sharkbite female connectors with 3/4 NPT threads on the other ends. All I need to do (gulp) is cut the pex as cleanly as possible, so that only about 2" or so is left at each connection. The portion of pex that will still be attached to the water heater needs to be no longer than 3.75" from the center of the check valve so that when removing the valve this can rotate without hitting the underside of the bench.
Then, Lowe's also carries a braided SS hot water hose that would connect to these two fittings.
I really love Lowe's because I get a 10% vet's discount on every purchase.
That's the plan and then I can put it all back together. If it leaks when I'm done, which is normal, you will hear me swearing at it wherever you are. Also normal.
Here are some more photos of what I have done so far.