Update to my original problem, new valve is in, I took it wheeling today, had no issues with heat (it was 90+ outside) nor with any head warpage.
So first what I did was bypass the old valve with a 4" long 3/8" MIP brass pipe from whole despot and flushed the fluid. That looked fairly clean which makes sense since the PO did the water pump and timing belt about 10k miles ago. I got the engine up to temp (about 190) several times and burped the fluid and the drained, just like Tim's video.
I then swapped in the new valve but I dropped the mount by about an inch. I have a 1.5" body lift so I'm guessing that plus wheeling caused more stress on the old part where the engine hose comes into the valve. I just used a basic flat bracket and a stainless screw and lock nut to attach the bracket to the valve first, be sure to bend the tab out of the way. Then attached the whole thing to the firewall using the existing bolt.
See picture links below, everything is running great, I drove an hour to go wheel, idled and wheeled for about 3 hours, then drove back home. Thanks to endive for all the help.
BTW, I'm cheap, so I got a basic Bluetooth obd2 dongle and set up an alarm on torque app to keep a closer eye on the coolant temps. The scan gauge sounds nice but I don't need that and don't need the additional features. My runner is manual transmission so I don't have to monitor trans temps.
bypass pic
bracket pic
bend tab out of the way
all our back together