So to me it's obvious that Leia had to be 3 or 4 when Padme died.
Which means Padme survives Episode III and dies 3to4 years after the events of episode III, and Obi-Wan takes luke to the Lars after birth.

I don't "know" Padme dies, and if you do, please use spoiler tags to conceal any info you have on ROTS. Some of us want the story to unravel before us in the theater, not on some internet message board.

If Padme dies or wether Ani knows about his children are MAJOR plot points in the film. Please be considerate and use spoiler tags where necessary as per the TOS agreement of this website.

But everything else Obi Wan told Luke about his father was bullshit, why should the lightsaber story be any different. I imagine Obi Wan will just pick up Akakin's lightsaber after their confrontation, just so the audience can make the connection with that scene in ANH. I don't think the statement "Your father wanted you to have this when you were old enough" is anymore truthful than "He betrayed and murdered your father". Hell, they way they act in Episode II, "He was a good friend" is really stretching the truth.

Imagine what sand would do to that respirator thingie he wears.

That one is easy. Lucas didn't decide to make Vader his father until after the first movie was released.

Ding ding ding! We have a winner!

So who was Darth Vader going to be originally?

Now I don't buy all of the explainations that Lucas currently gives about always intending this or that, but I do believe he always intended Darth to be Luke's father. There are a lot of subtle cues by Alec Guiness and the guy who plays Owen.

Subtle clues? Like what?

I've always thought it's been extremely obvious that the Darth father thing was some "revelation" that came up during scripting/filming Ep. 5.

It's just far too clumsy with the way things are said.

Vader's real identity was something that Lucas toyed around with back and forth before settling with what we know now. He even considered not revealing it until ROTJ. In early drafts of TESB, Vader & Anakin were two completely different people.

A New Hope:

Beru: "He (Luke) has too much of his father in him."
Owen: "That's what I'm afraid of. (Because his father is Darth Vader)"

The book "The Annotated Screenplays" says they brainstormed a scene where Obi Wan introduces Luke to the ghost of Anakin on Dagobah. Read the book. There was no plans towards any sequel (or prequel) other than "We hope to make a sequel". The movies were completely made up as they went along. It's in black and white. Now that's not to say they didn't have an incredible epiphany when they did come up with such ideas as Vader being his father, but he didn't have an overall plan for 6 (9-12) movies from the start. Knowing this, I find it silly to pick apart every line in the movies (first one, especially) and expect complete concordance. Even Tolkien had to go back and rewrite part of "The Hobbit" to allow LOTR to work.

And another point is that most of the lines in A New Hope could be interpreted in different ways. They are vague, and there were probably a number of ways Lucas could take the Trilogy and still make it work. Heck, he even wanted Han to sacrifice himself for his friends in Empire, but that idea got changed as well.

"He's got too much of his father in him" could mean what? At one point, Lucas wanted Obi Wan to be Luke's father. Obi Wan was a crazy old man according to Uncle Owen, and that would be sufficient enough to say that was what he was afraid of. It was a vague enough statement that no matter what Lucas came up with, people would have gone back and heard that line, and gone, "OH, that's what Lucas meant!" I doubt if Obi Wan was Luke's father anybody hearing that line would have concluded that truly meant that Luke's dad should have been Darth Vader.

I don't know if it's in the doc material or from a seperate interview that Hamill did, but when George told him that Leia was Luke's sister, Mark's reaction was:

"You made that up on the drive over here, didn't you?!"