I was home schooled from First Grade, until Freshman year of High School.
Pound him with math, math, math, and sciences. Biology, chemistry, etc. even if the levels seem "beyond him" you'd be truly amazed what a child can learn.
English composition and Grammar, and Math, from 1+1 etc. all the way up to Algebra and Trigonometry. And pound in the sciences. Human Anatomy and Physiology, Chemistry, (even Bio-Chemistry) etc. grind it into him. A lot of text books are self explanatory. Since you're a Nurse, you can help him understand certain things.
Just don't get into political stuff. Let him develop his own view of politics. That said, don't baby him, or "coddle him" from the rest of the world. Let him explore.
At age 15 when I had entered High School. I left High School with a Washington State Certificate of Academic Achievement. As well as several Principal Honors Awards, etc. etc. And I only attened a grand total of 5 years in the public school system. Trust me on this, his brain can handle all that.
Also, a very large barrier you're going to have to find a way around, is the socialization issue. If there is a boys and girls club etc. even a community church or whatever, let him go to those kinds of places, even to just socialize and meet people his own age.
Home school is incredibly lonely. You have no idea. psychology, and sociology and also concepts to have him learn. seriously.
Understanding how people react to things may help him when he re-enters the school system for High School. DO NOT home school him during his HS years. Those are the years he actually gets a nationally recognized Diploma, as well as has the ability to gain those experiences.