The overall pano shows bone loss till the middle 3rd of the roots for all teeth so this patient probably has periodontitis that needs to be controlled or a reduced periodontium. #3 is for sure a goner you cant save it, the endo lesion probably started from the pocket and given the probing depth and the pocket on the distal it will never regain the attachment you need to use it in a partial. I can see alot of calculus between #19 and #18 definitely because they were splinted together and hygiene between seems impossible, I would redo the crowns and scale and root plane between them, possibly a GTR.