The WP Reading settings does’t work for Portfolio module. It only works for archive page.
There is not the Pagination option for the list layout layout of Portfolio module. The load more button should not be shown, it is strange. please leave your wp-admin(url/user/pass) as private reply, I’ll log in to check it.
Please try to edit this Portfolio Module, set List Type as “grid list”, you’ll see “Post Number per Page” option, enter a number, like 12, turn back “Custom Grid”. It is a bug, the option of “Grid list” should not works for “Custom Grid”, we’ll fix it later.