I believe the stand alone form builder should work in CS6. It just won't work in CC versions of Dreamweaver.
You can use any gallery you want and set it up to work with CMS. None work directly with CKEditor, but you could have them add the images through CKEditor. I'd probably suggest using an hour of premium support to help you with this once you have identified the gallery you want to use.
This is what I think would work best:
1) Get your CMS working for other content on your site
2) Identify the gallery you want to use
3) Get the gallery working with static images the way you want
4) Set up a 1 hour premium support ticket with us and we will help you get the images and descriptions for the gallery from the CMS