After looking at your code, looks like you are also missing property for .setTotalItems(total_articles?number) in below code.
<#assign pageable_item = webuisupport.paging.pageableItem.setCurrentPageNumber(pageNum).setItemsPerPage(pageSize).setPagingMode("enumerated").build />Your code should be like
<#assign pageable_item = webuisupport.paging.pageableItem.setCurrentPageNumber(pageNum).setItemsPerPage(pageSize).setTotalItems(total_posts?number).setPagingMode("enumerated").build />Where "total_posts" should be the total count of the posts in the API results.
