Finsweet has their own forum for supporting FS products, it’s paid but worth it if you’re using FS attributes regularly on projects.
FS Items per page in FS CMS Load is a fixed number per page I think. You can get fancier constructions with the FS API and custom code. I’ve built a responsive version of FS pagination that way where I can have a different number of items-per-page at different breakpoints, you should be able to do something similar for your setup.
Hers’s the solution I found (just so that it is documented):
I separated the list into two sections (3 items on pageload = section 1, rest of the items = section 2).
Section 1
In the first section I set the item limit to 3:
After that I set the section 2 to display: none so that on pageload it only shows section 1 with the first 3 CMS items.
Then I put a “Load more”-button right under Section 1 that reveals section 2 when clicking on it.