After the final battle I had read that you could return to the world map and complete unfinished quests. When I finish the game and the movie plays and the dialog at the tree is complete, I am returned to the load game screen. Is this an end game bug or is it normal?

Normal. You can't go back to the game once the final battle ends. You are wisked back to the Elven City and get the grand hero treatment (a la Star Wars), after which you see the end movie and credits roll!