Hello,

Thanks for the feedback.

1.  Does your VideoJS plugin work with Piwigo's virtual albums, or not?

Never tests, I don't use it this way. You are welcome to test and feedback.

2.  In your documentation at https://github.com/xbgmsharp/piwigo-videojs/wiki you have a "semi-auto" procedure.  It says to "create a new album" in the Admin interface.  But wouldn't this usually result in a virtual album?

I never test it but a virtual or normal album should not have any impact.

3.  Then it says "Upload your video into the new album" -- how can we do this upload?

You can upload the video to your gallery the way you want. SSH/FTP or via the PWG web GUI.

4.  Is there any way to use Piwigo's HTML or Flash uploader to upload videos?  Or must we always go outside of Piwigo and use something like ftp?  (I see there's a File Upload extension that is no longer compatible.)

Yes you can use Piwigo's HTML or Flash uploader, here is no limitation, but never test.
IOS Mobile application only allow photos upload.

5.  Is there a way to make the film effect and autothumbnail settings in your plugin's Synchronize tab "sticky", or do I need to re-select them (and turn off Simulation) every time I run it?

It is not possible as of today, you have to turn-off simulation. This is the way PWG works on sync. For all sync page the parameters are reset to default.
I will try to change this behavior.

6.  Is there any way to get RegalAndroid or the Piwigo Android app to upload videos?

I don't know about Android or RegalAndroid.
You are more than welcome to feedbcak on those topic

Ideally, I'd like to be able to use the regular Piwigo uploaders from the PC browser, and/or an app on Android, to upload a video and then wait as your plugin generates multiple thumbnails, adds the filmstrip logo, places the video into any gallery, and automatically launches any necessary synchronizations.  Is that possible yet?

It is the main goal of the plugin. More than happy to work with you so we can each the goal.
Hope this help. I will do my best to update the documentation with your feedback.