T.,
As a parent, all you can do is guide your child. Don't be too hard on yourself if he's not doing what you'd like him to do. He is the Self he was meant to be and he will have to learn to navigate himself on his own. All you can do is offer suggestions.
My best friend has two beautiful children who have autism, one has aspergers, with the other it is more severe. My second oldest has shown signs of Asperger's his whole life. From puking up his food just because at meal times and not being to keep eye contact, to his personal range of sensory issues, and social difficulties.
As a matter of fact, my brother in law (now a teen) has Asperger's as well, and he is doing great. I'm so proud of how far he's come in the last few years. Autism is not a sentence, a "normal" happy life is still more than possible. We all have our ideosynchrocies, people with Aspergers just have a few more, or more pronounced. :)
With my own son, and with my best friend's children too we've found that the kids do much better when the adults in thier life are aware of what is going on and working to help them without stressing that they're "sick" - just approaching it as "this is what you're doing" and it needs to be dealt with. And also stressing their personal responsibility for their behavior. It is harder for a child with autism to control thier behaviors, some of them will be out of range of control without medicine, but it is important for them to still try. They will be stuck with themselves their whole life, it's important to help them learn to deal with themselves positively. I work hard with my son to help him recognize his own "warning signs" and react accordingly. For example - he talks with a certain "tone" in his voice just a few minutes before he gets too carried away to control himself. He used to be a big hitter, and now he bites his finger to maintain control when he wants to hit someone. Not that that's my favorite method, but he came up with one that works for him. He is in second grade right now and doing the best he's ever done (though he still spends half the month with his name on the board and has trouble turning in his homework) he has even made his own friends this year (a big deal for him! He was always asking why no one would play with him) and even has a *girl* that likes him. His teacher is very sensitive to his sensory needs and I think that makes a HUGE difference! My school district stinks in general as far as helping autistic kids, but my friend in the Roseville area has helped advocate for many families and they have GREAT programs out there. If you ever need to vent, feel free to message!
And as far as being over protective, I feel I am being that way sometimes too, but it is very normal when your children have had health issues early on especially - it sort of trains you as a parent from the get-go to think "is this too dangerous/risky for my little one?" "will they be OK?". My sister was very very sick as a child - she was a preemie, on a ventilator for quite awhile, had MANY, SEVERE allergies (two typed pages that included such nebulous things to avoid as "cold items"), Reflux, and Asthma. The doctors all told my mom until my sis was about 10 that she would likely die and my mom shouldn't get too attached, and should prepare herself for the probablility. (My sis is 24 and fine except for still having some allergies, and migraines occasionally) my mom felt a *tremendous* sense of responsibility for making sure her child made it, a tremendous sense of fear that my sister's health would fail on "her watch" and struggled with those feelings for a long time. So I guess I'm just saying, being overprotective is perfectly normal in your situation, so don't beat yourself up over it. Besides! Over protective parents make wonderful advocates for thier child's well being when the child is in need of one! :)
As far as making other parents understand, not everyone will. For a long time I just told strangers who looked annoyed by my son's behavior that he had neural difficulties - and this seemed to evoke a fairly compassionate response - more so than some other ways I tried of explaining things. Just take comfort as best you can, no matter how embarrased you may feel in the knowledge that you are doing the best you can to help guide your son and help him be the best, healthiest him he can be. Also, my best friend just started a special vitamin therapy with her sons (her doctor had pshawed this course of treatment a few years ago, so she did it sans medical advice) and they are doing GREAT! The amount of medication they have to take has lowered dramatically and she feels that they may eventually make it off the meds. (The same doctor was so impressed and excited by the results, she intends to sell the vitamin course from her office and has begun treating other patients with it) I will find out the name of the supplements if you like. Just let me know!