How to increase or maximize power to a certain level and level intervals in both early, mid game for different types of main characters? having limited resources.

i have some questions:

1. In tank equipment upgrade, it says upgrade to chunin - forehead, chest, and book? Or it's only a typo which should be ring?

2. In the formation, main > tank > DPS > support, why is the main in-front of a tank? Isn't the main gonna die very early?

thanks for the awesome guide this helped a lot