Fullback rules

Coaches, I wanted to get your input on rules for your fullback on the pure inside zone, inside zone lead, the offtackle zone (basically the inside zone a hole wider) and the outside zone. I know alot of teams have their FB go backside to seal the DE on the inside zone and go outside for the force player. Also, with his rules, what do you tell him on how to get there, like if he is supposed to lead through the B gap but there is a tackle in the B gap. What adjustments would he make in those situations?