Your first graph shows Democrats had a worse rising homicide rate. Fail there.
Graph 2 and 3 are an indication of a few things, one of which I will address in point #3. For this point though, you do "well" on the graphs if you either A)have next to no one in your state to commit crime or B)have so many people in your state that the huge numbers of crimes being committed is covered up on a per capita basis because of that large population. There is also a bit of my last point at play here too.
You asked about the Mason Dixon line and why things look so bad in the south and the inconvenient truth is the percentage of the African American population us larger down there. If you took your 4th map and juxtaposed it to a map showing the percentage of African American citizens in an area, the high homicide areas have a direct correlation to the areas with higher concentrations of African Americans. (Which coincides with their homicide rates being astronomically higher than every other racial category in this country.)
And yeah, yeah...how racist! I don't think you can address a problem without acknowledging it exists. The black community has a violence problem. That may be for a host of reasons but it is what it is.