Thanks for getting back so quickly.
I tried what you suggested and it helped to some extent.
It works as long as I copy and paste the link directly to share on facebook.
Both problems persist when I use the 'f' button on the gallery's button bar to share. The files are still cached somewhere but I can't figure where. Right now, all I can think of is to disable the button bar.
I also have another issue with the button bar - it never completely aligns to the center of the image. My pet peeve.