The following are only my opinions, but with my experience trying to advocate for my son in Florida schools, I'd advise the following:
First, apply to DYS immediately.
They can help you advocate for your son, who is exceptionally gifted, and they can help you figure out what kind of educational environment is going to work for him. That said...
Second, consider homeschooling.
Your DS has a much better chance of finding kids he can connect with and relate to in mixed age groups and in groups that self-select for giftedness than he does in an age-grouped classroom. It is also extremely unlikely that he is going to get an appropriate pace and depth of learning in a regular classroom, or even a GT classroom. His GAI is two standard deviations above that of the typical student in a GT program.
