Between cable modem and SF1005D, there is no router? If no router, at most one PC can access interent with a cable modem because a switch has no sharing function.

The SwitchPowerSaveTool is available here and it is proper for other models as well. http://www.tp-link.com/en/support/download/?model=TL-PA511&version=V1#tbl_b

Your W8968 is V1? You just enabled bridge on WR542G? As I know, bridage has to be configured on both sides. Can you enable WDS on W8968 and try to connect to WR542G to see what happens if possible.

YouView issue? There is beta firmware. If you need, contact TP-LINK support to get it. :) No need to return it. http://www.tp-link.com/en/Support/contact/

MA180 or MA260 should be proper if you need a 3G USB modem.

Suggest configuring it as an AP which can be configured the same SSID and security settings as the hub. The hub's Wi-Fi can still work.