re: was Jefferson Davis guilty of treason?

"I think he died in New Orleans in 1889 if memory serves me correctly, but someone can double check that."

He did die in New Orleans and you walk right by the house in which he died. It is not far from the shops and restaurants on Magazine Street.

"Anyway, was Davis a traitor?"

I say that he was not because in our federal system, especially as it existed before the Civil War, states are sovereign bodies and he remained loyal to Mississippi. By way of analogy, the break-away states from the USSR almost certainly had/have leaders who previously served in the Soviet Union. While Davis, for better or ill, chose Mississippi over the Union, he was not a traitor. (I would say the same about Southerners who chose the Union over their home states. Not traitors).

"Was he a hero?"

Difficult to say. From the accounts I have read, he was brave in the face of pursuit by federal forces, but ultimately, the secession of the Southern states was too motivated by the desire to extend the institution of slavery for me to regard him as a hero even if I admire him in some respects.

"Should he have been prosecuted and hanged?"

No. Many were on the losing side and I am not aware of anything Davis did as president of the Confederacy to merit such punishment, especially if you wanted to reunify the nation after the war.