I want to let you know that we have dealt with this issue intermittently throughout with DS7 (almost eight). I noticed that the issue ramps up when I am punitive and directive in my approach. Sometimes, I've had enough and will say things like "go to your room." or "this is unacceptable behavior, you have lost your screen time today." It lights a match to a powder keg, but it's hard for me to let go of these methods because it's how I was raised.
I have to go with with aeh on this one, and say that it's critical that you and DW have an agreement (ironclad) about how to deal with tantrums. Smart kids will quickly(!) figure out who is the pushover. In our house it's DH, god love him.
I will also say (this from a parent who has also seen her child a flailing hot mess long after most children have given it up) that it's critical that you work on coping skills for your child and for yourself. I'm going to direct to the one of the website that I have found incredibly helpful to deal with meltdowns, aggression, disrespect, etc. It's called Empowering Parents
http://www.empoweringparents.com. They have a product, and I'm not so interested in the product (that will be your decision), but they also have a wealth of articles, blogs, comment sections, etc. You will quickly find that you are not alone, that there are many households with challenging/struggling children.
I think that the Ross Greene book is good--and I agree that the sticker charts (been there, done that) did not work long in our house. Mine, was constantly seeking novelty- and there is only so much novelty that I will finance when he meets my request to put on his clothes
Sticker charts at school was another matter- they worked beautifully in that environment.
