I did not recognize most of the abbreviations but I fell you are suggesting the telephone wiring inside the house could be a source of the problem.
The following speed tests were performed using bandwith.com.
Telephone wiring as is; phone line >> Westell modem >> Netgear router >> computer smart TV via network
computer 1.29 0.37
TV 1.28 0.36
Wiring as is; phone line >> Westell modem >> computer
computer 1.28 0.37
*Domestic telephone wiring removed
incoming phone binding post>>Westell modem>>Netgear router smart tv via network
TV 1.28 0.36
* The incoming telephone lines are terminated in an unenclosed binding post. I removed the outgoing lines (domesic} and replaced them with 5 inches #18 solid copper wire and a standard telephone jack This was connected to the Westell modem followed by the Netgear router
I believe this eliminates all the inside objects with the exception of the Westell modem.
