During the reign of Manasseh in 2 Kings 21, tradition says that Isaiah sawn in two while hiding in a log. Is that true? Also, did Manasseh have other prophets killed?

In several places, our sages teach that King Menashe killed Yeshayahu (according to tradition, his grandfather!), so apparently it was common knowledge (exactly how, relates to the question how much midrashim are meant to be taken literally, see http://old.yeshiva.org.il/ask/nihul/Eadmin_search_ask.asp?srch=1&filter=&orderby=-1&q=are+midrashim+true&em=&nonAnswered=&cat=1). In M'lachim II, 21, 16, it's written that Menashe spilled much innocent blood in Jerusalem, apparently referring to the blood of the prophets, his monotheistic opposition, who rebuked him for idolatry, thus threatening his rule. This is alluded to again in Yirmiyahu (2, 30), "Your sword ate your prophets like a devouring lion".