OP - One thing is to see if you can get DS to sign the papers to allow you to continue to know about his health care and to help him find the best services needed. A good online FREE resource is the Special Needs Alliance to get you started to understand the aspects of a Special Needs Trust in planning. On health care at least he can continue on your family policy until age 26.
If he is making strides with anxiety and other aspects, I would start higher education locally to help him acquire daily living skills. Also if he has a therapist and psychiatrist he works well with it may be most important with the diagnosis at last to continue the team during this major transition in DS’s life. If he goes to college, I would look into insurance if available should it not work out. Just remember there is no one set pathway or timetable for a young adult, and the impact of the last three years needs to be considered, too.