Hi Littlebear,
I also work with young children. Some of the behaviors you describe can be considered normal for children of this age, however I applaud you for following your instincts and being persistent with getting support. In assessing a child, a pediatrician or other relevant health professional will hopefully look at your DS as a 'whole child' instead of behaviours in isolation and take many factors into account. It can be difficult to get a diagnosis even if ( and at the moment it's an if) there is a condition to diagnose.
You and your partner know your DS better than any professional. Remember that. You are doing the right thing in following through with your concerns and if you're not happy with what 1 medical professional says, a second opinion is always a option.
Hugs to you, let us know how things go.