Brandon, here are your answers.
1. You do not need to take a test and become a Certified Commercial Applicator to apply Fertilizer in Tn.
2. You do need to take the test and become a Certified Commercial Applicator to apply Pesticides/Herbicides.
Just study the 2 books you have and you'll pass the 100 question test. If you fail the 15.00 test, you can take it when you feel ready again; it's given every week.
Once you are a Certified Commercial Applicator, you are able to spray for someone who has a "Charter/License". After you have 2 years verifiable experience, you can take the next test and get your own Charter. When you get your own Charter, you can spray for yourself.
Everything I just stated is in your "Ornamental and Turfgrass Pest Control" book PB1652