It's like we need a crowbar to get our DS off the computer.

The only thing that works is the threat of no access tomorrow ...
You are right about chelation & most of the biomedical interventions for autism. More bang for the buck if done at a younger age. The main thing I know about chelation & regression is this: that chelation is fairly nonspecific, and it can remove the good guys (nutrients) as well as the bad guys.
There is a very heavy need for zinc in any adolescent boy's body, due to sexual maturation. The average ejaculation drains a big portion of a typical RDA for zinc. And it is a mineral that could have been chelated out. So, making sure your son gets adequate zinc in his diet is impt. My son likes pumpkin seeds & sunflower seeds, good zinc-y snacks.
I once heard a talk by Wm. Shaw, head of the Pfeiffer Treatment Institute, which has the largest database in the country, maybe the world, on the correlation between nutrition status & behavioral/psychiatric problems. PTI also has a number of NIH grants to continue study & analysis in this area. One of their findings is that low zinc status is linked to a more difficult, less sociable passage through adolescence, and more rebellion. As kids mature, their zinc needs stabilize & often low-zinc adolescents become "late bloomers."
The one supplement we all (including my DS) swear by is high concentrate EPA fish oil (not just any old CLO or fish oil). The EPA (my DS needs one to two grams per day of the EPA fraction alone) has a very mellowing effect on the brain. We've found it's helpful in reducing impulsivity, anxiety, obsessiveness, aggressiveness, and for increasing overall communicativeness/willingness to talk things through. If DS skips 2 days of his EPA, boy do we all know it! Carlson's & Nordic Naturals are 2 brands that have EPA concentrates that are 3rd party lab certified for heavy metals & contaminants, which are always a consideration in autism. There may be other brands as well. EPA has been found to reduce the need for medication in bipolar disorder, and in depression/anxiety. It's possible that your son could reduce some of his meds w/EPA concentrate. One note of caution: EPA fish oil must NOT be used by anyone with bleeding problems or blood clotting abnormalities.
Be careful w/the Prozac. The SSRIs, and prozac esp., are Jekyll & Hyde drugs. They often work well at first, but as the brain changes in response to the drugs -- receptors and/or receptor sensitivity decrease, aggressiveness and/or impulsivity can increase. Our son has had bad experiences w/SSRIs that way. Which is why we've come over to the more alternative camp. His experiences on meds were uniformly nasty, typically a short honeymoon followed by hell.
Good luck! Hopefully you'll get to hear from a few more folks.