Caroussel Comments

I would like comments posted to an image in a carousel to display before the comment prompt box

I’m afraid you’ll need to edit the Jetpack plugin files to do that, as Jetpack doesn’t offer an option to display the comments before the comment prompt. You can do so here:
https://github.com/Automattic/jetpack/blob/3.1.1/modules/carousel/jetpack-carousel.js#L106

I would like to have the event of those comments piped into the Latest Comments widget

WordPress’ “Recent Comments” widget doesn’t include comments from attachment pages by default. You can change that default behaviour by following the instructions in this post:
https://wordpress.stackexchange.com/questions/156608/display-attachment-post-and-page-in-recent-comments-widget