Tanzaku theme & Facebook link thumbnails

There’s a problem with this theme’s multiple thumbnails generated by the grid and Facebook. I am not sure which one causes the problem, facebook or the theme.
When I publish a link to my facebook page, it used to allow all 30+ thumbnails as a choice, but now it has been reduced and it differs: from 10 to 3. When I change the slug, the permalink, the available thumbnails come back to 10 and those are usually not the ones I need for the link. I don’t want facebook to have the control over which thumbnails to choose from, and it’s important for the facebook page link to represent the content of the post.
Otherwise the problem if continues, will affect traffic to my website, and it already has.

Before there was a debugger link available to fix the problem, which seems to exist in the permalink, for some reason. Now the debugger is not available, and facebook limits the number of thumbnails, which usually end up being taken from the end of the grid images, which are irrelevant to the content of course. Only sometimes the image from the actual new post is available as the first thumbnail.
I cannot use the featured image because I don’t upload images to my website, I store all of them on flickr, so that option is not an option.

Any word of advice, how to fix this problem of volatile thumbnail availability on Facebook?

http://wordpress.org/extend/themes/tanzaku/