Unlikely you'll get six months of freedom on an ED visa. These days you have to attend class at least a couple of times a week, and extend every 90 days. You'll get 60+30 off a SETV, and then with a border bounce another 30+30, so you're getting close to your target
Your volunteer foundation is the best approach. They have to complete the paperwork and assist with your work permit. Perhaps best to discuss with them