It's really normal to have these kids have scores all over the place. Don't panic.
My HFA kid is now 11 and will start middle school in Fall 2014. He's doing very well academically.
His scores have been all over the place. He took Iowa Basics tests at his private elementary. Some of those scores were in the 99% and some (listening!) were in the 3%. (Lowest 3% in the US).
He took a Cogat in 3rd grade at the same private school. They tested him one year above grade level because they wanted to see how he would do. For his age level, his composite score was 99%. For the 4th grade level, he tested 97%. His verbal reasoning scores were 92%. His critical thinking and math skills were 99%.
He has had a WISC twice. Once when he was first diagnosed, at age 6, and once when he went for an ADOS/ADI-R to get a formal DX of ASD, at age 9. Those scores were also all over the place. His overall IQ tests at 117 to 119, but he has some subsscores that test towards the 140-145 range and some subscores that test towards the 75-80 range. His first tester told us flatly that a WISC is not a good measure of his actual ability or potential because his score profile is so spiky.
In 5th grade, he has straight As and his teachers tell us that he performs well above grade level.
We rely on his actual performance as the best indicator of what he is capable of doing. We don't know how he will test for college entrance. It could be great scores and it could be crap. We'll take what we get. I would like him to start at a community college and adjust gradually to college, anyway, so scores aren't a bid deal. There are colleges who will take students at every level of scores and that will allow him to work his way into a good career no matter what.
For you son, who loves maps and navigation, a degree in geography with good GIS mapping skills can be obtained at a ton of regional state schools. Those skills are in hot demand and it pays well. He doesn't have to test that well to get into one of those programs. There is a pretty high demand for these jobs and they pay a solid middle-class salary for just a bachelors. If he wants to go further, advanced graduate work is possible.
http://money.cnn.com/magazines/moneymag/bestjobs/2010/snapshots/97.html
http://www.indeed.com/salary/GIS-Specialist.html
http://en.wikipedia.org/wiki/Geographic_information_system
I'm not saying that is what your son will end up doing. But I can easily see a successful future for your kid. Breathe. It's going to be fine. It is fine, right now.