With Windows Phone 7 devices, updates via USB were performed via the Zune desktop software platform. Unfortunately, with the discontinuing of not only WP7 but the Zune desktop platform, this option is no longer viable.
I can, however, propose an alternative solution if your computer is connected to the internet via wired connection (I'm assuming it is as you mentioned doing this without wifi...) Bridge your wired and wireless connections on the computer, and connect to your computer's newly-broadcasted network via wifi on your phone. Basically this is turning your computer into a wifi hotspot of sorts, allowing you to upgrade the software.
If you're relying on a public wifi connection to download the updates and then later push to the Lumia, why not just use the public wifi connection to pull the update on the phone directly? Another option would be visiting your local mobile phone store, as many of them have wifi you can use to update the device as well.
Equalizer settings in the Windows Phone 8 platform can be found in Settings>Audio.
MKV files are supported using Moliplayer Pro, however, as a paid option, I'd recommend simply using a free video conversion application such as Handbrake or Miro Video Converter. This will not only provide native file format support but will also reduce the file size. While you obviously want the maximum quality possible, using an MKV format on the 630 is a bit of a waste, as you won't see noticeable differences between the format on the 630's screen.
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