I want to use the rscomments for the whole items. So I paste the {rscomments option="com_k2" id="----"} into item.php

What I have to type for the id="" to get the item id

someone please correct me if i am wrong, but i think the {} code is the plugin code for the rscomments. it belongs in the text of the item, with the item id hard coded after the =
There would be a completely different way to plug it into every item via item.php
Search the rsjoomla forums for that method