Incongruities in Star Wars - Just For Fun

Star Wars is playing on Spike TV as I type. I'm sure others have asked these types of questions, but I can't help notice incongruities in the whole series

• How is it that Vader noticed the presence of Obi Wan in A New Hope and missed the presence of Luke when he knows Luke is his son and felt his presence in The Empire Strikes Back and The Return of the Jedi? He even sensed that "the force is strong in this one" in the death star battle in A New Hope.
  
• Obi Wan gave Luke a light saber in A New Hope that he claimed his father wanted him to have when he got old enough. There's nothing in The Revenge of the Sith or any of the prequel episodes to give an indication that Anakin even knew about his children much less provided for their tutelage in the Jedi arts. In fact, he and Obi Wan didn't exactly part on best terms. It's kind of hard when Obi Wan dismembers Anakin and leaves him to die smoldering just next to the lava flow. Anakin's last words to him: "Hey, Obi Wan, take this light saber and give it to my son when he's old enough - Senator Paladin has forseen it. Oh, I'm sorry, I can't seem to find it, much less hand it to you right now..." I don't think so. Perhaps Vader looked Obi Wan up later after he got his new prosthetic limbs. "Hey, old master, give this to my son..." Then, the next time they meet, he tries to kill Obi Wan without so much as a, "Hey, did you ever give that old light saber to Luke like I asked you?"
  
• If Vader did indeed know about Luke, why didn't he know where to look when they were searching Tattoine for the droids in A New Hope? He should have told the storm troopers, "I know where the droids are going. I feel his presence here as well as my son's. Find Obi Wan Kenobi in the desert outside of Mos Eisley and you'll find them."
  
• If Vader could sense that Luke was his son in The Empire Strikes Back, why didn't he sense that Leia was his daughter in A New Hope? Why don't we hear Vader say something like, "Leia, you must learn the ways of the force. The Emporer has forseen it."
  
• Why didn't C3PO remember Obi Wan or Tattoine in A New Hope? "Oh my, R2, this is where I was built!" and later, "Obi Wan, sir, it's been a long time! What are you doing here at Tattooine?" You don't hear anything like this.
  
• Why didn't R2D2 remember Yoda in The Empire Strikes Back, especially when Yoda didn't tell Luke who he was? *R2 tweets excitedly when Yoda comes by.* "Familiar you look, my friend," Yoda says. Luke whines, "R2! What's gotten into you?" ...It never happens.