There are no "published benefits" for separate PNRs and separate tickets. You get the standard benefits on each of those tickets, but they are - and will always remain - two separate tickets. You can never "engineer" them into a single connecting itinerary, having purchased them as two separate tickets.

Protection is, in general, intended only for passengers on connecting tickets.

There is no way to "link" separate PNRs that achieves the same outcome as having booked all that travel under a single reservation. ("linking" PNRs is effectively merely sticking a post-it note on the file - which may or may not ever be seen by anyone - and only informs the reader that there is a separate ticket that the customer wanted noted on the file; it does not get you, nor does it entitle you, to any of the benefits that you would receive if all flights were under a single PNR. It's effectively meaningless, but it seems that some airline agents acquiesce to the request, if only for an easy life and because it seems to satisfy the person asking for it to be done)