youtube-dl supports downloading videos through a proxy, by setting the http_proxy environment variable to the proxy URL, as in http://proxy_machine_name:port/.
Using the -f option and other related options, you can specify the video format to be downloaded from YouTube. If you have an order of preference, specify the formats separating them with slashes: -f 22/17/18. Instead of keeping a video format table here, I will refer you to the list of YouTube formats on Wikipedia.
Using the -f option and other related options, you can specify the video format to be downloaded. Add the -F option to see all valid formats. If you have an order of preference other than best quality, specify the formats separating them with slashes: -f 22/17/18. You can also pass in an extension, like -f mp4/webm.