Definately change those images to something really HUGE and let them keep linking...
change it to say something like:
IMAGES AND CONTENT STOLEN FROM WWW.EXAMPLE.COM
Then let google know about it, blast those sites with DMCA violations. Having your images still hot linked and stating that they are yours will surely give google the information needed to wipe the walls with them.
Sadly, Google has a tendency to like freshly found content over anything else... not fresh as in new, but fresh as in they just found it.
The sad part is that you will likely need to rewrite your content and put them on a different page, leave the original so that Google can verify it's yours, I wouldn't touch the original page until Google has had time to assess the situation.
When you rewrite the content, imbed your url somewhere in the middle of it. Most scrapers don't take the time to look for that ... they just scrape and go.
If it were me I'd lose the RSS feed or somehow find a way to imbed your url into the middle of it as well. We ditched ours a couple of years ago because of a similar situation.