Re: If the Moon were replaced by other planets...
At 384,000 km, I think the Earth would be within the orbit of Io, which interacts significantly with Jupiter's magnetosphere. It'd be outside the main radiation belts at 100,000 to 140,000 km though. Spacecraft tend to avoid going closer to Jupiter than 300,000 km.
"After a time, you may find that having is not so pleasing a thing, after all, as wanting. It is not logical, but it is often true." -- Spock -- Flip flap!