We never said that Xander can do no wrong. Heck, Xander does lots of wrong. Some fans like that because they think characters like Tara, for example, are boring and unreal because they're always sweet and nice. Characters like Xander are more real because they have flaws. That doesn't mean that I support Xander's flaws. I relate to some of them, but don't support them.
I guess you like Buffy, right? Is she by any chance perfect? No. She makes a lot of mistakes, and she can be selfish and immature. That doesn't make her a bad person, it only makes her real.
I don't think he cared about Angel. I just think he cared a lot about Buffy to push away his dislike of Angel and be supportive and as I've showed you, he did a nice job being supportive after Revelations.
That doesn't mean he wanted him dead. If he did, he would have cheered Kendra on when she suggested they kill Angel. He didn't. Actually, he kind of defended Angel by saying that he's their friend. Xander only wanted Angel dead when Angel turned evil, before that, he never did.
I don't know, why would Buffy be nice to Spike after he tried to rape her? There's something called forgiveness and acceptance. After Him, Xander didn't badmouth Spike once. In fact, the examples I posted show that he was okay with him around.
But he only hated him after he turned evil. Disliking Angel didn't mean that Xander wanted him dead. He wanted Angel dead in Becoming more because Angel was dangerous and less because he was jealous. I don't even think jealousy had anything to do with his lie.