this is just rough but you will see what i mean
Code:
function split_content($content) {
$content = get_the_content();
$content = apply_filters('the_content',$content);
preg_match_all('#<p>(.*)</p>#Us', $content, $m);
return $m[0][0] . $m[0][1] . $m[0][2];
}
add_filter('the_content','split_content');
will split into 3 paragraphs if you have 3 in your post, obviously you would have to check how many, then you can hook in whatever else is needed, etc.
hit me up and i can get you sorted.