Hello,
In order for r4 to consider r3's loopback, or any other address redistributed by r3, is reachable via an rsvp lsp it checks it's ospf database. The issue here is that the routes from r3 are received in r4 by an ABR and not by r3, because they are on separate areas. In this case you can use the FA's that were recommended by other users previously, this will help because you will get to see the routes directly from r3, not via an ABR, and LDP requires and IGP route to match.