Add a "footer" to each group?
If you need nid of current node as token, then just add Content: Nid in field list, and check exclude from display before saving it. Move this field at the top of the list &amp; you will be able to use it as token in any other field under Rewrite Result. 

But if you want to use nid of entityreference field as token, then you need to a Relationship under Advance tab in your view. Then after follow the same process which I explained in first paragraph. But this time you will have to use your added relationship.

For custom Add More link, just add Global: Custom text in field list &amp; put HTML for this Add More link.