You got a powerline extender kit? WPA4220KIT? The default Wi-Fi password of the extender is on the back of bigger unit? It is composed of 8 digits. To change Wi-Fi name and password, you can login...

It is OK if powerline adapters can communicate with each other in your environment. In the home office 150 ft away, only one room or different room have to be covered by Wi-Fi? Maybe powerline...

Place powerline adapter in the same room and check the rate on your PC. If it is the same, try to replace them under warranty.

When connection drops, how about status of all lights on powerline adapters? Have a check. Try to use two working units to replace them and test if the problem disappears. Disable power saving....

You may need to update xbox app to the version for Windows 10?

So you want to use W8968 as an access point with DHCP disabled? It is quite easy... Reset the W8968 to factory defaults first. Change wireless SSID and password. Change its LAN IP to 192.168.0.2....