The edits you mentioned here should be pretty minor, as it’s usually just a matter of changing a value in the code to change the number of images per row in your example.
Ideally, we’d like to be able to do more to help out here, but as this is not a Shopify theme it is not our code and so we wouldn’t be able to interfere in even a minor way without potentially causing further issues.
Hopefully, some other members of our community will be able to pitch in from their own experience and may be able to help out.
I’d advise you to leave a link to your store here so that any helpful merchant or partner who is willing to help out can check this out with you.
Otherwise, I’d advise you to get in touch with the theme developers who will be able to comment on their level of support.
You said your store had yet to open, do you know what you need to work on next in the leadup to the big day?
I’d recommend our store launch checklist in any case as it’s a great way to ensure you’ve got everything ready to go for launch.