Hi Matt.
I'm close to your age, I also have two sons with autism, one severe, one not as much. I hadn't been quit from dip for more than 30 days prior to joining this site.
My advice to you is to post roll every day, as soon in the morning as you can, and get involved with the community. That's your best chance for a successful quit.
Is ABA therapy an option for your son? Both of mine get 35 hours per week. We haven't had an hour-long melt down in a long time. Things aren't perfect, but much better.