Like conspiracy theories typically are, this one is full of holes:
- Darth Vader was not in command of the Death Star; Grand Moff Tarkin was.
- Darth Vader didn't build R2-D2; that droid was built before he was born.
- There is no record of Darth Vader having children.
- The exhaust port was not two feet wide: it was two meters wide; there are kids on Tatooine who can hit a target that size from a skyhopper.
- If the Imperial intelligence services had been doing their jobs properly, the schematics for the station would never have fallen into rebel hands in the first place.
- If every single gun turret on the station hadn't been designed to shoot at cruisers with no regard to the possible threat of fighters, the rebel attack would have been quickly repelled.
- If the exhaust port had been fully shielded instead of just ray-shielded, there would have been no rebel attack at all.
We should be glad he survived instead of trying to blame the Death Star fiasco on him.