I don’t see where you’re trying to insert these rows, but given what I so see. You’re going to need to adjust those counts, $total, $pages, $min, $max, to account for those extra rows you want to insert.
Personally, I would look at this
$items = get_field('slideshow_items');
This is actually returning an array with all of the rows. I would then insert my extra rows directly into this array using the same format and then to all of the work based on the new array. You can see what’s in it by
echo '<pre>'; print_r($items); echo '</pre>';
once you’ve added your new items then you can loop through the array rather than using the have_rows() loop
foreach ($items as $item) {
// slider
}
