We have done both partial and full homeschooling, with good success. #2 was around your DS's age when we did partial at a tiny private school, which consisted of one to two days a week at school, and the remaining time at home. We picked the days that had "specials" (art, music, phys ed, computer, project day). DC participated in academics with the class on school days, but was not graded on them, and understood that we would do "real" academics on the at-home days.
Currently, we homeschool full-time.
You may wish to inquire at your district offices regarding homeschooling options. In our district, residents are allowed to participate in any amount of in-school time as homeschoolers, as long as it does not comprise all academics (this is to prevent families who use nominal homeschooling as a way to avoid state-mandated testing, while receiving all of the services of public school--a curious thing, btw, since parents almost always have the (possibly little known) option of opting their students out of testing). Your state and district will have their own policies.
With regard to your own degree of confidence: you know your child better than anyone else. There are many resources that can help you school him according to his own learning profile and pace. WTM is a good resource, as are the posts on the Recommended Resources page here. And keep in mind that his current situation appears not to be meeting his needs, so it's not like you would be short-changing him by what you would do instead! Summer is also a good time for low-key experimentation with homeschooling, maybe for an hour or so a day. You'll find that most learners, especially PG learners, won't need a full six hours a day of homeschooling to cover more than reasonable expectations. At the age of your DC, we've historically expected about 2 hours of homeschooling time 4-5 days a week, and found it to be quite adequate for keeping our children engaged in learning, and moving forward at a pace appropriate to their needs and abilities. It also leaves lots of time for interest-led activities and creative exploration.
