Everything you describe, plus your history, suggest asthma or chronic bronchial inflammation (possibly due to SLE), with some residual right lower lobe congestion that probably needs to be broken up by regular, therapeutic breathing treatments. Since your cough is productive but not bloody, it may be you've developed an autoimmune variant of pneumonia that's become chronic. This can even be a mild form of bronchiolitis obliterans organizing pneumonia (BOOP), which is often missed in tests because of its unique nature (no infection, yet it mimics mild to severe pneumonia without most of the systemic signs such as fever, that would normally be seen). This and othere similar sorts of chronic interstitial lung disorders, are often treated successfully with steroids.
It would seem a consult with a pulmonologist may be in order. The pleuritic pain can accompany almost any sort of lower respiratory infection or psuedoinfection, and may linger for quite a while even after the acute problem has resolved. It would help to have even a broad diagnosis ("could be A, B or C) rather than just having a lot of possible causes tossed out and no attempt to narrow it down and get it resolved.
Hopefully this is helpful to you. A more thorough workup is required to get to the bottom of the problem. One way would be to test for SLE and rule it in or out. Another would be to have a bronchoscopy done to see if that RLLL congestion is actually BOOP, which sometimes must be biopsied (or at least a specimen obtained) in order to identify it, since it creates a unique sort of almost cellulose-like material instead of ordinary mucus.
Best of luck to you with this, and please do follow up as needed.
John Kenyon, EMT, CCT
Non-invasive cardiology tech, Emergency and Critical Care technician, Critical Incident Stress Mgmt. specialist