I think you put a lot of thought into this.
Regarding point 1, Your scenario is as good as any. Another possibility is that Leah may have referred to her adoptive mother as her real mom. Or Leah may have retained some memory of being in the womb or of birth and sensed her mother.
Regarding point 2, I think the viwer is left to presume that at some point between episode 3 and 4, Obi Wan learned the power of immortality from Qui Gon Jinn.
Regarding point 3, Vader didn't ask about the baby because he may have felt in his premonition that the baby had died. At that point, he may have realized that the death he forsaw and he sought to prevent, to the point that he had given himself to evil, was actually caused by his own hand. Palpatine / Sidious looked as if he was feeding off of Vader's anger. He may have chosen to tell Vader only enough to fuel Vader's anger.
In any case, I don't think these points merit an Episode 3 1/2.
I thought the acting was good, but bone of it was oscar worthy (with the exception of General Grevious, I'm kidding).
Did you catch a glimpse of the Millenium Falcon? I thought I saw it in the mid-to-lower right corner of the screen during one of the daylight scenes of bustling city.
You make good points. I just personally would have liked more actual continuity to the next 3 episodes...
I still think Christiansen was incredible this time!