Good questions and I really appreciate the great input. It is my son who has done his research and is quite clear that 4 years more is just too long. He will need to work on the History, Politics, Econ and writing, but Math, Biol, Chem, Physics, Calc, Algebra are college level. I recognize there will be no easy match for social peers in college, but have observed far better interaction with college age and level of maturity than high or middle school kids.
We don't have great high school options where we live. There are a couple of community colleges that do a good job at dual enrollment, so this is why I'd like to think of that as a second option.
Long term college entry is a better option than dual enrollment. The exit age will be legal with career plans and program of interest.