I’m afraid we’re in a bit of a jam. From the information we’ve seen so far, it appears that the dbpath is a bit messed up.
The message /var/lib/mongodb/journal/WiredTigerLog.0000000015: handle-open: open: No such file or directory we saw earlier basically means that WiredTiger requires that file to be present to be able to start successfully. The fact that this vital file is missing seems to suggest that the dbpath was tampered with in unexpected ways, unfortunately.
Thus looking at the information so far, I would suggest that the best way to get MongoDB to start again is to start from scratch with an empty dbpath, and restore from a last known good backup. I’m sorry it has come to this, but I don’t see a productive way forward at this point other than a fresh start.
Best regards
Kevin