Yep, you can post into existing campaigns, and no the tool has no limit, but FB may suspend your account if you go too crazy with it. I've had no problems posting ~200 per day.
I feel compelled to come here and give a review of this product. It works exactly as he describes.
I LOVE this tool. It makes it so easy to create and test facebook ads. At this point after using it for a couple days it would be really hard to go back to manual submission using the facebook interface.
I've added a pause/resume type feature. This allows you to easily create ad batches to post over a few days or you can even post just one ad that might need reposting.
I also have a mac version in the works so if anyone wants to test this let me know.