Man that config is long and scary...
The way you're reading the magnetometer looks fine. Just to note, it's not going to give you degrees, but rather, magnetic flux. The data sheet says the values can range from -4096 to +4095 (13-bit signed integer). 4095 represents 1229 µT, and 1 represents 0.3 µT. (micro Teslas) Unless you use a magnet, you're not going to see any readings near those extremes.
http://mythopoeic.org/magnetometer/
It's been a while since I've messed with this stuff, but there is a NOAA calculator that you can use to get an idea of how strong the magnetic flux is in your area.
http://www.ngdc.noaa.gov/geomag-web/
I wouldn't expect anything over 50 µT in our area unless an external source is applied (such as a magnet, motor, electromagnet).