I seem to see less contradictions in these lines than you do.
"Your father wanted you to have this [lightsaber] when you were old enough, but your uncle wouldn't allow it."
Obi does say "this weapon is your life." to Anakin, and though they both got spare lightsabers in AOTC's climax, it's still not unreasonable to think lightsabers are plenty important. Mace has a custom one, as does Dooku.
Obi-Wan is also lying a great deal to Luke about Luke's past. This is probably partly because he's ashamed of his own role in what happened, and partly to protect Luke. it's one thing to learn your a Jedi, it's another the same afternoon to learn your dad is like, the worst person in the galaxy. Maybe Obi would have told the truth had he survived the Death Star.
"[Uncle Owen] didn't hold your father's ideals - he thought he should have stayed behind and not gotten involved."
Obi lying. See above.
Princess Leia refers to some recent galactic history:
(to Obi-Wan) "Years ago, you served my father in the Clone Wars."
Considering all of the seperate conflicts, political ramifications, culteres and governmental bodeis involved, I don't see why pluralizing "Clone Wars" would be totally unexpected. It happed in the Indian Wars of US History.
Obi-Wan does say his loyallty is to the Senate... to Democracy! So it's also not totally unreasonable to say he served Bail Organa, especially given that the entirety of the war takes place off screen, who's to say he didn't serve him specifically at points.
From ESB, Obi-Wan directs Luke to the Dagobah system:
"There you will learn from Yoda, the Jedi Master who instructed me."
"Mrs. Iglesias is the teacher who instructed me." That's true. I don't see why I need to add "...when I was in 3rd grade." Especially when I'm talking to someone dying in the snow.
Yoda and Obi-Wan discuss Luke's potential:
-"You are reckless!" (didn't he mean, "Reckless, are you!"?)
-"So was I, if you'll remember."
We never saw Obi when he was younger than 20 or so. He might very well have been wreckless, especially when he was a wee lad in Yoda's tutelage. Even at 20 he had a bit of attitude to QuiGon.