I can see exactly what you mean. The product is very large when you click into the product page. The themes are built different and this is how Boundless is presented. You could reach out to our support team directly to ask our theme support team directly if this is 1.) Possible and if so 2.) worth doing as it could be very custom to completely change a structure of the theme. You can contact our support team by clicking and logging in here.
The other question I have is are you completely tied to the Boundless theme or would you be willing to explore other options with something more to what you like already in place. I took a quick look and the Brooklyn theme has something closer to what you're looking for:
You can see the full list of free Shopify developed themes here.
We have a new product template for boundless themes, with a lot of features that allow you to redesign your product page as you like, you may be interested in it.
One of the available options on our template is displaying product images with thumbnails.
You can check it and see all the available features in it from here: