Would this TPR valve set up work in the hot water line like this?
For pressure yes for temperature No
TPR valve probe should be located with in the top 6" of the HW tank
And where is the visble point of termination after it enters the sidewall?
Good question, I could not find it and the crawlspace access has been covered by new laminate flooring. Could not gain entry to see anything in the crawlspace.
Not only that but if you look closely the expansion tank is installed with a tap valve, it was just dying to break off when touched.
It might “work”, but not as intended.
If TPR leaks by it could create humidity in the crawlspace
The TPR sensor must be inside the tank and within 6 inches of the top of the tank. The TPR discharge must comply with these http://www.nachi.org/tpr-valves-discharge-piping.htm
What did they do with the TPR valve that came installed in the tank?
I bet that TPR is old enough to vote. Doubtful it is even functioning if it were installed correctly.
TPRs must discharge to an air gap in the same room as the water heater.