Hi flower. Reading your post my heart goes out to your son. I'm 27 now but suffered exactly like your son did for most of my school life. I can count the happy moments of school on the fingers of one hand, and the effects of the bullying I experienced lasted well into adult life for me.
Obviously, as other people have said, you need to address his feelings of depression. I have no experience of medication but have been very depressed at times and know its no fun. This, and ensuring he reaches his potential in education, needs to be a priority.
I want to reassure you as well that there is hope. For a start having a diagnosis will help your son understand himself a lot better. I only discovered I have AS a few weeks ago, but even before this I have gained a degree, held down jobs and long term relationships and have a number of very good friends. People say 'kids can be cruel' and its a vast understatement, but please don't assume that your son will always be treated the way he is being treated now. He needs to know this as well. There are many environments where he will shine in the adult world. A lot of people say AS is a disability, but I personally see it as a gift, albeit one that caused me a lot of problems before I learned how to use it to my advantage. There are probably a lot of people here who would agree, and who also live lives far more fulfilling than the majority of the population. Be there for your son and encourage his talents to their full.
I'd also like to share a theory I have that your son might appreciate too. Its about the times in people's lives that they reach their peak. Generally, I believe its better to peak later in life (which most people with AS do). Most of the people who were the 'top kid' in the playground have never grown out of it and are unemployed or cleaning toilets for a living now. The ones who were losers at school have generally made something of themselves.
Hope this helps.