I don't get the prompt to remove pictures once I unclick the sync box.
You uncheck the "Sync Photos From" box in the Photos Tab and then click on Apply in the lower right corner of iTunes, and that should remove all synced photos from the iPad.
Without knowing anything else that you might have done, quit iTunes, restart your computer, reboot your iPad and then try again.
Reboot the iPad by holding down on the sleep and home buttons at the same time for about 10-15 seconds until the Apple Logo appears - ignore the red slider if it appears on the screen - let go of the buttons. Let the iPad start up.