The mime types were mainly for getting sound to work, but black screen usually means it stopped with a java error. Probably not recognizing the filetype.
Do you have a "webconfig" file in your root directory?
here is a clip of the start of mine, it has a bunch of other junk in it you wouldn't need.
<mimeMap fileExtension=".ogg" mimeType="audio/ogg" />
??<mimeMap fileExtension=".m4a" mimeType="audio/mp4" />
If you don't have access to one, ask your provider about adding a couple mime types, they may have to do it for you.
Here is a tutorial page:
you might go ahead and stick:
<mimeMap fileExtension=".webapp" mimeType="application/x-web-app-manifest+json" />
under the audio types, if you ever submit to Firefox marketplace, it needs that one.