You'll need to research and analyze every last Noble in Europe to see what kind of things they'd do in reaction to history changing from OTL.
That's overkill IMO. Identify the major players, who and what and where they were and what they were doing when the PoD happened.
Then work forward with knock-ons. Throw in the odd butterfly for authenticity. (Changes of births and deaths, mainly.) Avoid butterflies that are too convenient.