That actually looks really good! Even with the land. I think the problem is that there is too much detail so it's hard to draw it back to a handdrawn look.
I was trying out Snap Art as well, not sure about long term functionality but I got some great effects using the snap art filter results as adjustment type layers, I was using Google images as a basis. (freind of mine asked me to do a campus map for a Humans vs Zombies game)
I set the base map to 33% overlay over the background parchment. I ran the impasto (i think) with one of the small brush settings on a copy of the base map and set the layer to Soft light, 100%. Third layer was the base map run through Pencil Sketch, I think it was small pencil no canvas and set that layer to multiply 66%. I couldn't leave well enough alone, had to try multiple filters at once ;P
My finished maps
"...sometimes the most efficient way to make something look drawn by hand is to simply draw it by hand..."
Looks good, but still looks shopped to me....but then I guess I know what I'm looking for, not sure if people who don't use photoshop will!
I took the liberty to run your map through pixelbender (I really hope you don't mind) so you could get an example of what it would look like. I think it gets rid of the satellite-sharp look in a good way. The left side is with pixelbender/high pass on and the right side is your original file. As I said just an example for you.