Issue with gallery ID and blog posting

So I’m working on a horizontal scroll WP website for my girlfriend here (wip location):
https://leighmcd.com/blog

I’m having some issues with adding a custom gallery as I don’t want to have div’s inside the post (ideally). The gallery is loaded by posting a shortcode (Ex. [print_gllr id=123] inside the text field but in order to get the styling to show up I have to wrap it with DIV’s.

I was trying to load it outside of the text field in the index.php page but that didn’t work.

I also tried making a Custom Field where you just enter the gallery ID number but since it’s being called by shortcode I don’t know how to adapt it to just php.

Any advice would be greatly appreciated.