Conventional current flowing in the opposite direction to electrons causes a huge amount of unnecessary confusion. See Was Benjamin Franklin wrong (about conventional current)? and Does electricity go from negative to positive or vice versa?

For the rest of the questions, you need to be clear on a circuit; there must be a complete path through the battery, wiring and component in order to operate. Fuses are placed in this path such that excessive current causes the fusewire to melt, cutting the circuit and halting flow, rather than any of the wiring melting (which would start a fire buried inside the panelling of the car).

(In some ways, the important thing is the electrical field transmitted through the wiring that causes current to flow. Using the water pressure analogy, if you have a series of pipes and apply pressure to the end of one, it will be transmitted everywhere in the pipe system even if the water isn't flowing.)

Conventional current flowing in the opposite direction to electrons causes a huge amount of unnecessary confusion. See Was Benjamin Franklin wrong (about conventional current)? and Does electricity go from negative to positive or vice versa?

For the rest of the questions, you need to be clear on a circuit; there must be a complete path through the battery, wiring and component in order to operate. Fuses are placed in this path such that excessive current causes the fusewire to melt, cutting the circuit and halting flow, rather than any of the wiring melting (which would start a fire buried inside the panelling of the car).

(In some ways, the important thing is the electrical field transmitted through the wiring that causes current to flow. Using the water pressure analogy, if you have a series of pipes and apply pressure to the end of one, it will be transmitted everywhere in the pipe system even if the water isn't flowing.)