A lot of these diagnoses can be confusing because so many of the symptoms can be indicative of more than one condition; that can mean that a misdiagnosis is possible, or it can mean that more than one condition is occurring at the same time. Worse, sometimes the medications can create additional problems or reactions, which either reduces their effectiveness, create new problems, or alter the proportion of some of the behaviors so that the original diagnosis is called into question.
There is phenomenal work being done by multiple research institutions with various funding sources, and all are pointing to significant benefits from nutritional help to offset the many causes of these behavioral issues. There is likely a an environmental component (chemicals, processed foods, toxins in our surroundings), a pharmaceutical component (not just the drugs themselves but some of the components and fillers added to pills during manufacture to bind them together but keep them from sticking in the molds used to shape them), and a nutritional component (mass growing techniques and harvesting patterns to increase the year-round availability of foods, and therefore increase profits, but without putting real nutrients and trace elements in the soil - resulting in large and beautiful looking crops with far less nutritive value than nature would provide.
These factors are a huge part of the reason we see incredible increases in the types of problems you list (ADHD, impulse control issues, communication issues, sensory issues) but also the massive increase in food allergies over the past 20 years. So the research has identified a number of nutritional issues, and some simple changes that can be made to reduce these behavioral problems. A lot of diet philosophies are based on elimination - take out dairy, wheat, soy, nuts, and everything will be perfect. While that may address, short-term, some allergic responses, it doesn't get to the core, and it's incredible difficult to follow.
Instead, research has shown that actually adding nutrients in a balanced form (not one by one, in isolation), can make a phenomenal turn-around in focus, attention, rage, outbursts, impulsive actions, sensory issues and a lot of the anxiety and depression than can come along from a body being out of balance. There are also changes in the epigenome - the packaging around the genetic material in each cell - from all of the chemicals and environmental influences. These cause changes in gene switching (which genes turn on and off), and that affects how the cell behaves, functions and replicates. Nutritional advances are showing extraordinary repair of this gene switching, which helps brain cells and nerve cells (and others) return to normal, preventing diseases as well as behavior problems.
We are seeing kids like your son start to turn around in sometimes as little as 2-4 weeks with nutritional support, and the benefits grow over time. If you'd like to explore this (which will not conflict with any medical course you choose), I can connect you with some on line, in person, and webinar-type resources to help you learn more. There is help for your family, and it's often faster, cheaper and more responsive than medications, testing and evaluations.