A great problem in ROTJ and the OT is the handling of the fact that Darth Vader is Anakin Skywalker. Ben's from 'a certain point of view' argument is weak. Also everyone seems to remember Anakin as a great hero not the child murdering scumbag he actually is.
My solution is this:
Darth Vader is Obi wan's apprentice. He is called Darth Vader since that is his name (Darth is not a title for sith lords). Anakin is a full jedi knight and a hero of the republic.
Darth Vader is tempted by the emperor and the dark side and eventually becomes a sith. He starts helping the emperor to hunt down and destroy the jedi. Ben and Anakin lead the war against the emperor and vader. This war culminates in a duel between Ben and Anakin vs Vader overseen by the emperor. Vader is winning and all will be lost. The galaxy will fall into darkness and also Padme (and his unborn children will die).
In desperation Anakin is tempted to use the dark side to kill Vader. He does this but is unable to come back to the light. Ben realises that Anakin is lost and will now replace Vader as the emperors new henchman.
The emperor orders Anakin to kill Ben and they duel. Ben wins the fight and flees but Anakin is hideously disfigured. The emperor does not wish the public to know that his champion (Vader) has been defeated so he has Anakin suited up and calls him Darth Vader. No one can see his face, so no one will ever know. The emperor will let it be known that Vader killed Anakin and forced Ben to flee. He will say that Vader was hideously disfigured by the cowardly jedi and must now wear a mask in order to stay alive.
This satisfies the following continuity problems.
Darth Vader was a pupil of Obi Wan who turned to the dark side.
Anakin was a full jedi, not a padawan.
Darth Vader kills Anakin. Well not quite, but that is what the general public think. Only Ben knows the truth. When Luke questions him about it he can truthfully say that Anakin was a great jedi and a great friend. He wanted to shield Luke from the fact that Anakin turned to the dark side in an attempt to defeat the real Darth Vader).
Anakin is still remembered as a great hero by the general public. Only Ben knows the truth that Vader is Anakin.
The real Darth Vader (not Anakin) can kill the younglings although I would not have that scene in at all.