Well, I'm not either, but your problem sounds similar to one I've had,
when I export a drawing as a jpg or png. The Export window has a
menu for Background, and either Black Background or No Background
might be causing your black image.
Truncated text -- just guessing here -- might be related to
permissible pixel dimensions, or to the middle popup menu, for Just
Graphics, Selected Graphics, Full Drawing Area etc. My last step
before exporting is to draw a rectangle around my graphic, "framing"
it as I wish, and on Color & Style unselecting Outline. That gives me
an invisible frame, and when I export as "Just Graphics" I get a
border of white space.
In your example, unwanted white space above your favicon might be
causing the app to truncate the image's bottom edge. Do a Select All
to see if you have an unwanted invisible graphic lurking above or
below your image.