I have destroyed Akulakhan and there has not been any kind of dark brotherhood assassin. I have gotten the ring from Azura and the cutscene played. Do I have to go to Mournhold by console commands?
I am also not sure if this is a glitch or if it wasn't added into Morroblivion but after you beat the main quest I remember people calling you Sera or Nerevarine not Outlander.

You have to sleep and be at
You have to sleep and be at least level 14, too.