For most of your questions, it'll be easier to just implement the points. Then you'll see.
I am using terms more familiar to myself indeed, and it can become quite complicated to explain them further. So I appreciate it if you can just leave them as my own self notes for now.
That being said, the "enabling to come back to the same page" I meant as if each auto loaded "page" was an actual page and then, if you click on an item, when you press back you can get back to that same "page" and see the item on the whole listing.
I figured an easier way to get a similar behaviour and we'll go with that, so I'm not going to implement it the way I had envisioned (which is like it's done on discourse) this time. It will simply open products in a new tab.
Now, there is 1 topic left that I'm glad you brought up. The layout.
I also like the way the current shop looks, but I can't just implement pagination on top of it at all. There are only 2 ways to do it. The one I did, with using script to load the json, and using a different template, the ideal of which is the "Developer Platform" (which should actually be called "template developing").
In either way, the more we develop, the more we will get. And, as I told you before, the U$321 price was to do the minimum, and that's what I'm doing.
Going with developer platform requires more effort, so I never cover it in this minimum price. While using scripts make it harder to tweak layouts. So I won't be able to get the layout exactly as it is done with shop.
I think the way it is now it's pretty close. And it does have this extra feature in which you can choose the width of each product thumbnail to allow for more than 2 columns.