Damn, You got it! As you can see, I'm not really good with these "riddle" things, but it was fun to try.
1. "Son of the bear" is Ulfric, son of the Bear of Eastmarch.
2. "The falsely accused" is Wuunferth the Unliving, who you falsely accuse of being The Butcher.
3. "These halls of old where man first came" is a reference to the fact that Windhelm is the first city in Skyrim built by humans.