Welcome. Please do a sig for yourself when you are ready, it will save you having to describe your family over and over, every time you post. It helps us keep track so we can better direct any suggestions.
One thing I highly recommend - read "The Explosive Child" by Ross Greene. It gives a different way of looking at your child, leading to a different way of parenting. I found it made my life a great deal easier and has reduced the extreme touchiness and reactivity of difficult child 3. The discipline techniques can be used on any kid (I actually keep it in mind when I'm dealing with education authorities - I have a theory that large organisations, notably our welfare authority in Australia and our Dept of Ed) are themselves autistic - they have communication problems, they are extremely rigid in their thinking and in the way they expect us to interact with them; obsessed with rules as they interpret them; they're not good at playing together. You may feel some of these also fit your son - it helps to know that he could have a great career in public service!
Read around this site also. Browse trough the archives. We are simply parents of kids who are a bit more challenging than most. We have a collective experience level, however, which is a very powerful tool that is now available for you to use, to help you with your family. In turn, you may find that someone else has a question that you can answer. Don't panic if you feel that will never happen - trust me, the day will come when you realise you have your own diploma from the School of Hard Knocks.
Nothing is ever a waste. Life is all learning experience. And if I can use my experience to help you, then it won't have been all for nothing.
Marg