WMG for Wyrd Sisters. Warning: Potential unmarked spoilers.
The last name of Hwel, the dwarf playwright from Wyrd Sisters......given who he's based on. and assuming he has one, has gotta be Spearshaker.
Verence IIwas the bastard son of the Queen of Lancre. Because of the way it had been implied that the young Gytha Ogg "committed treason with a leg of mutton" (assuming "his life above stairs" was an Unusual Euphemism, and not literal). The Land accepts him because he acts properly kingly, rather than like a gluttonous, mad, or otherwise unfit usurper.
The History Monks are aware of Granny's use of a Timey-Wimey Ball but have not intervened.As pointed out in the main section, the Discworld timeline is a bit dodgy. To answer the question whether the History Monks had to fix up these events in any capacity, perhaps they did notice, but thought that everything has turned out as it ought to be (for a given value of 'ought to'). That gives them a spare fifteen years that nobody was using, which might be useful somewhere (or somewhen) else. Besides, the Monks know an immovable object when they see one, and wouldn't be game to confront Granny directly.