Re: As far I can understand
2) The actual republican gain was +2.72%, the drop in margin didn't reflect a republican gain, it reflected votes moving to a category that they chose not to report.Or am I completely misunderstanding this?
Seems to me that you understand perfectly. That map is pretty bogus. Have a look at York County, Virginia. It seems a bit of a stretch to say there was a Democratic shift of +3.56% when Hillary actually got a smaller percentage of the votes than Obama did in 2012. It's clearly an indicator of a shift to third party candidates but the MSM likes to pretend they don't exist.
Romney: 59.51% - Obama: 38.83% - Margin :+20.68% R
Trump: 55.22% - Clinton: 38.11% - Margin: +17.11% R
Shift since 2012: +3.56% Democratic