I would start the cost reward system with all privileges in tact. And for your son, you may need to really try hard to find the smallest of the smallest positives and provide a ticket. Going this route will ensure behavior modification any day over negative consequences which just result in power struggles. Even if you say good morning and he isn’t rude. TICKET. Sometimes you have to start very basic.
Also keep in mind behavior therapy especially with children takes a very long time to change behaviors. 2 months is an extremely short amount of time to assess change. If you have concerns schedule a parent meeting with the therapist.
I have an adhd son in 3rd grade it can be hell sometimes. Keep fighting.