I see what's happening:
The code will not work for unequal product heights especially with masonry setup. You must set all product items to a fixed height.
Then it will display like this:
This is the furthest I could go. I already went above and beyond for this. I also said this is only a hack. If you wish this to be a part of the theme, we'll list this as feature request instead so it might be taken into account in the future. For now, this is the farthest we can do.
If you wish to have more options, please consider using one of the bundled grid plugins as they allow a different number of column per screen size. Please see the items below:
Thank you for understanding.