Roof edges need structure, airflow, and water control to agree.

Because that is where water spends the most time. A gutter that overflows, leaks at a seam, or slopes the wrong way keeps the timber behind it wet for days after rain, and paint fails long before the wood does. The rot is the symptom; the cause is almost always drainage or the edge detail where the roof meets the gutter. Replacing the fascia without fixing that just resets the clock.

Not by itself. Soffit vents are the intake half of a system, and adding intake without matching exhaust at the ridge moves very little air. It is also common to find the new vents blocked from above by insulation that was never baffled away from the eave. Attic heat is usually an air sealing and insulation problem with a ventilation component, in that order.

Yes, and only over sound wood. Aluminium or steel wrap over fascia is a legitimate finish that removes a repainting cycle; over deteriorating timber it hides the deterioration and holds moisture against it. The board underneath has to be sound, replaced where it is not, and photographed before the wrap goes on — because afterwards nobody can tell which of those two things happened.

Partly. Getting the animals out and keeping them out is pest work, and it comes first. Repairing what they damaged and closing the entry properly is carpentry and roofing. What matters for the roof is that intake ventilation is restored rather than sealed over in the process, which is a common outcome when an opening is simply blocked up. Agree who is doing which part before anything is closed.