Rick made the wrong decision about Tyreese's group, though, but it was all about him being crushed by responsibility. It's significant that he was about to change his mind when Laurie appeared. His subconscious can't deal with more potential guilt.
I don't know. Rick was only half
-wrong about Tyrese's group. Two of them were already plotting to jump Carl and Carol and seize control of the prison.
seen that Tyrese is a decent guy who wants to do the right thing, but Rick has no way of knowing this. He hasn't seen what we've seen.