For #1, I don't believe so. The Map object does not currently support coloring 'by expression' (just dimension, measure, single color) which is what is probably needed. This is available on other chart types, just not a map . Refer to 'visualizations that support color by expression' at :
For #2 , i tried a variable and/or measure and could not control a measure friendly name for the legend. In the end i disabled the legend title and went with a chart 'subtitle' see below on a left side legend to approximate this. Not perfect but might be acceptable.
For #3, i could not get this to work with an Area (KML) map. Just a point map as follows
Lastly, you may have already seen this but there are some nifty KML options available through the new 'geographical functions'. I didn't see these until a colleague pointed them out so i'd thought i'd do the same. There don't resolve the above questions but still enhance what you can do with KML in Qlik Sense out of box.
Perhaps in the back end somehow. The 'color by expression' would be very helpful to display a 2nd measure on the map. Its been asked for a few times now. Hopefully we add support in the not too distant future.
So... if you find a technique be sure to share because it would be helpful