"see what the power is at each point"...
Right at the antenna connector on the TX radio. 48w
At the end of the TX cable where it connects to the duplexer. 18w
At the duplexer antenna output before the cable. 20watts
At the antenna end of the coax. Can't, it's 40' above ground.
"I can’t diagnose it if it’s not really what you’ll be using."
Yes, I'm testing the same equipment, Coax, duplexer and antenna I'll be using.