At 20,000 miles, no smoking or carpool in my car, do I need the following: cabin air filter, fuel injectors cleaned and brake fluid flush?
None of this needs to be done at the dealer if that is where you got these recommendations. The cabin filter you might be able to do your self and also the air filter . You Tube will have videos showing how it is done. Fuel injectors I would say no. Brake fluid I and others here say to do that every 3 years .
Also look in your manual as it is the best source of what service you need.