The downloading is due to the mime-handling in your browser, it's acknowledges itself as an rss+xml file and will most likely result in a download.
I see what's up with your feed.
Why I have no clue, but the site-url variable in the database is not changeable in admin but the images path and the rest is, blatant mistake.
You need to change the config-table in the database, update the siteurl so that it has http:// in front of your url.
The second thing is the time.
I'm not sure if it will qualify as a time or if it will throw errors.
Where do you want it, only in the rss-feed or for every single image?