Hi Cristian. I am not an employee of the support, just a user as you. But let me explain how it works, so that you would not waste your time.
I am not familiar with this template, but the study of code accurately shows what is happening.

- This is addon Thumb gallery
- This is a special addon, the Product Button that displays a piece of the J2Store form. But it can only display the form and nothing else.
Addons are not dynamic and cannot transmit information from one to another. Therefore, with this layout you will not succeed in achieving what you want.
If in the Unei Product Button settings, it is not possible to display a full-fledged product card, with the behavior as you want, then you need to use a product card from J2Store by default without using SP PB. And customize its appearance through CSS.
Using Sp Pb inside J2Store is half a fake product card, as it does not possess and cannot have a full-fledged store functionality.
That is why I completely refused to use J2Store + SP PB and I use JoomShopping + сustom сoding in my projects.
Perhaps I do not know something about J2Store + SP PB integration. In the forehead case, this is my private opinion.
And the support team can confirm or disprove it.