He says he's a king's man. If Ulfric wins the war, he's making weapons for Stormcloaks and says it's all the same to him.
They did? The Markarth Incident is one year after the end of the war. If they were involved in setting it up, then they were at work right afterward. Even if they're not telling the truth about that, it was only shortly later that they intervened. Talk to Igmund.
It was veterans, not generals, and General Decianus was acting against orders.
Again, this is not true. All humans and elves are descended from the Ehlnofey, and the Nords mixed with Nedes, but Nedes =/ Nords. This is falsehood spread in early PGE's and was controverted by developers Kurt Kuhlmann and Michael Kirkbride. And again, it doesn't matter.