It’s something that you can do, but will take a lot of work as most of what you want to do is not documented and there are very few examples that exist.
You’ll need to add custom JavaScript to ACF https://www.advancedcustomfields.com/resources/adding-custom-javascript-fields/
In the JavaScript you’ll need to detect changes in the repeater sub fields and then you’ll need to update the value in the tinyMCE editor where you want to put the gallery field.
Alternately you could create a custom shortcode that could be inserted into the gallery where the shortcode gets the values of the repeater and inserts a gallery into the desired location when displaying the field. https://codex.wordpress.org/Shortcode_API
