OK, here's where I am:
On Windows 7 Home Premium, I have the Google Chrome browser with the Google Cast extension installed. Also, in the Windows Control Panels -> Network and Sharing Center -> Choose Homegroup and Sharing Options -> Choose media streaming options, I have "[TV][LG]60LA7400" set to "Allowed".
On Apple iPod Touch, I have the following Google apps installed: YouTube, Chrome, and Chromecast. I also have the LG TV Remote app installed and paired with the TV.
I have successfully gotten the iPod's YouTube app to cast video to the TV, but I have not yet had success with the Chrome or Chromecast apps. From Windows, I have gotten the Chrome browser to cast a video from YouTube.com to the TV, but it's very finicky. The Google Cast extension is only occasionally recognizing the TV. This is huge progress, though. I still don't know if videos from non-Google sites (e.g. CBS.com, Hulu.com) will ever work.
I followed your setting and have the same experience. Can cast from youtube (Chrome or iphone), but no TV is shown on the Chrome cast button.