TP-Link AC1350 Wi-Fi Range Extender Conflicts with AT&T Universe TV Reception

My client bought this range extender that uses his households electrical wiring as a method of connecting the houses router/modem to other parts of the house. His router is in the bedroom near the front of the house. When he is out on his rear porch, and streaming music from his iPhone, using the house's Wi-Fi, it cuts out a lot. He decided to try the TP Link but after he set it up and used the WAP button on the Wi-F- to clone it into his present network, it worked 'OK', giving him 'better' reception near the inside back of the house. The TP link device was inserted into an outlet on the rear wall of the house. He got better streaming inside and outside but nothing great. Then he turned on his living room TV and the RP link interfered with the wifi of the TV to the WiFi in the bedroom. He disconnected the TP links and all was better with the TV. Any ideas on how to resolve the 2 problems?
1, get a great signal outside the house so he can stream from his iPhone to a wireless speaker?
2. have no inteference with his TV.