I think I can help, but I won't be able to look at this for a few days. In the meantime, make good, safe copies of everything to a backup folder. Maybe even to another computer.

All should be well. I have dumped, deleted and restored specific conversations from this database before, and I am familiar with its tables and their schemas. If you're tech savvy and ambitious, I encourage you to familiarize yourself with the sqlite3 command line tool. It will play a big role in the restoration.