First you need to make sure all battery connections are clean (no corrosion) and secure (tight)and the battery is fully charged with battery charger
second you need to understand that some components do not have fuses.
They have circuit breakers and fusible links
Since the starter won't crank with the key there are few things that could be the problem.
NSS (neutral start switch) is preventing power to S terminal of the starter relay (solenoid) on the fender.
Try this and get back to me