If you want a long life expectancy, try to find a job that fits your abilities. Stress in the workplace is usually the #1 cause of stress for most people, because they aren't in a position to escape it.
It is easy to set your expectations in life too high, and if what you do in life does not meet others expectations try to focus on the fact that your health is more important than doing a job that doesn't fit your abilities.
I didn't know I had Autism at your age but I did know that my potential to handle stress was not extremely high. After getting three degrees I got a job at a Government
Bowling Center for 18 years. The whole time I worked there people told me oh you are so smart you can do better. Looking back, staying there in that low stress job, is the best decision I made in my life. It made all the difference in my quality of life. Eventually I was pushed into an extremely stressful job, and it burned me out in about two years.
There are some interesting topics on this website about how Autism affects older people. Many of them do experience some sort of burn-out in mid-life and it is usually from living in a stressful situation too long, that they are not able to manage. It also can happen at a younger age, depending on the person and situation.
One of the best things you have going for you is caring friends and family. Positive social relationships, in general, are the number one factor in happiness and research shows that these relationships play an important part in longevity.
The fact that you exercise is also extremely important; it is natures way of burning off excess stress chemicals. Unfortunately some are not able to physically do it. If all you do is walk everyday that will be a tremendous help. The important thing is to stick to something you can do your entire life, if possible.