Sorry my advice didn't work for you. It is what I used to do back when I did have this issue (not just in RV). I have played RV a lot as it is probably my favorite EA town, but I have never had an issue with Hogan's Diner *knock wood.*
I do use Overwatch and Error Trap though so I have not had any problems like this for a long time now. I thought a patch had addressed this issue, but maybe I was mistaken and it is just the mods that take care of it.
It should not mess up your town to just delete Hogan's Diner. Unless there is a grave/urn on the lot. If someone died there and their tombstone/urn is still there, you would want to move it to the graveyard before deleting the lot. HTH!
ETA: It occurs to me that you may have a stuck social jig in the way that is making it difficult for people to leave. Unfortunately, without Twallan's mods, I do not know how you would even check for it or get rid of it.
