hashbrown: The 7 months of some isolation is not by itself an issue. I work with many back-yard dogs where they were cute puppies tossed into the back yard, then dumped at the shelter when they were no longer cute enough, typically near a year old. The are scared of people, adult dogs, other animals and everything else in the world. Yet most come around within a few months. Many of them in 2-3 weeks.
But the first question is whether you have taken your dog through basic obedience training. If not, I'd suggest you look for a dog trainer who is comfortable with these issues. Taking into account, however, that their purpose is not to train your dog, but to train you to do the work.
Also, the aggression you described is likely fear aggression. But, you didn't say if he slightly backs up (defensive), or if he's ready to charge forward (offensive). This is usually anxiety based, simply because he has no experience and doesn't know what to do. If this is offensive or if he panics, you need to be very careful with him. Eyes immediately rolling back could be a panic issue where you should seek help from somebody experienced with this issue.