>> If Vader knew of Leia, why did he so vigorously react when Luke accidentally disclosed her during their battle? His renewed vigor in that fight shows he was learning something new. With two children, he had two chances at turning a partner to help in defeating the Emperor and becoming the Sith master himself. Anakin’s pride again on display. He was always fighting to better his teachers. <<
Vader was reacting to Luke’s renewed vigor... and having tapped into Luke’s anger.
>> Luke was smug when brought before the Emperor because he was convinced he could turn Vader by then. It was a look of “I have already defeated youâ€. <<
Essentially, this is correct, but agrees with my argument: Luke knew that there was good in Vader. We’re only quabbling about the magnitude and nature of that realization.
>> Anakin only made 3CPO, not R2D2. And when he last saw the droid, he had not been given outer skins yet. There were many protocol droids that looked like 3CPO. No reason for him to know him. <<
Plausible, but how prepostrously unlikely is it that Leia happens to grab the robot Anakin made?
>> Obi-wan had been a hermit and focusing on the connecting to force at a greater level for years. He knew that Vader striking him would be the impulse event that would transform him directly into The Force - hence no body. Even Vader had a corpse at death. Obi-wan and Yoda did not. <<
Impulse event? Not canon, then it didn’t happen.
Luke only grimaced when Vader said "a sister" and remained silent and in hiding. He knew he had slipped up and disclosed her. It was not until Vader threatened to try an turn her to the dark side, should he fail with Luke, that Luke responded in anger. Vader provoked the response with the threat to Leia. Luke didn't react first.
Luke knew there was good in Vader because he had begun sensing that while training with Yoda. Yoda confirmed it's existence, but warned him it would be risky to try and bring it out. It is why Luke allowed himself to be captured. He had become convinced he could do it.
Impluse event? Not canon, then it didn't happen
Obi-wan was purposefully maintaining a stalemate battle with Vader until he saw that Luke and the others were going to make their escape. At that point, Obi-wan stops fighting, holds up his saber in a ceremonial pose, and says "strike me down, and I will become more powerful than you can imagine".
Sounds like he is talking about an instantaneous transformation, caused by Vader striking him. Call it what you will. But I would say a quote from the movie could be considered "canon".
Only two characters die without a corpse: Obi-wan and Yoda. Their "deaths" were notably different events.