What is the difference between standard and enterprise versions of the module?

The standard license of a DNN module allows to install the module on one web domain and one DotNetNuke® installation. The module can be installed on multiple DNN portals as long as they run under one web domain.
The enterprise license of a DNN module allows the module installation on multiple web domains, multiple DNN installations and web portals.
Also here you can get more information about the license.

I can't upload my video file to the server

Please make sure you added video file type as allowed extension to your DNN portal (please see the user guide). If you are using DNN File Manager, there might be a restriction for the size of files you upload. Use FTP if you are uploadign a video that is larger than 6mb.

Player keeps spinning buffering icon but doesn't play the video

Please make sure your video extension is an allowed MIME type on your IIS. To check this, just try to access the video via browser navigation bar. If you are getting 404 error, that means IIS doesn't have a MIME type for the extension of your video file. You can easily add it following this guide.

How can I format the Gallery Page layout?

You can use CSS and create a specific container for the module. If it's not enough for you, you can change anything in ascx file (layout, structure, etc.)

What kind of YouTube URLs can I use in your Video Gallery?

YouTube should look like these ones:

http://www.youtube.com/watch?v=jn1t0gonqws
http://www.youtube.com/watch?v=j-fWDrZSiZs

You can get them from browser's address bar on YouTube website.