Never got to the stage with DS you have, as I grew up with a challenging sibling, but have seen other adults do so on occasion.
. I agree with the "explosive child" rec'.
If you can get there the charity Ambitous about Autism does genuinely useful courses in challenging behavior for HFA/teens/girls/those kids others seem to ignore. They are based at Treetops in N.London (10 mins on the tube from London Bridge).
They helped me when noone else could,(or would) and have continued to give me ongoing advice over the phone at times. I can't praise them highly enough, as they seem to dare go where noone else does. www.ambitiousaboutautism.org.uk/page/what_we_do/training/training_programme.cfm
Linda Miller wrote a book "The five point plan". It's based on using traffic lights. I've also found this incredibly helpful. she's a very smart EP who specialises in the top end of the spectrum and those with "olympic ring" diagnoses. Very,very helpful if you can get her face to face.
"123 magic", (another book) is I am told fantastic with adhd kids. It certainly works with DS's 3rd cousin. However I found it no help at all with DS (AS/sensory). It's worth a red just in case it does help your son as he has a duel diagnosis.
Don't beat yourself up.You are in uncharted territory & the important thing is to recognise that your isolated behavior on one occasion isn't the answer. If your child is late for school on the odd occasion is it REALLY the end of the world? Sometimes if it takes plonking yourself and the child on the floor in the middle of the pavement for 15 minutes till they calm down then that's what has to happen for everyone's safety.
DO deffo keep a diary listing all the triggers for challenging behavior including environmental (smells, noises, scratchy clothes, wide open spaces, time of day, place etc). it's amazing how a couple of months (or weeks if you are lucky) can help you identify the triggers. Once you know the specific trigger to a really challenging behavior you are 90% of the way to sorting it, even if it takes months of slow, steady plodding to help the child resolve it.