Helicopters can't be loaded onto Carriers. You could change this in the editor. As for the rebase range, it's 3 or 4 times it's operational range. I think it's 3. You can also change this in the editor by increase it's operational range. This is only in Conquests/Complete. Vanilla and PTW, it's unlimited rebase range.
Helos are kinda weak units. They're only really good for rebasing troops into a city that needs defenders quickly and you can't get them there that turn. They can recon too, so that's sorta helpful. But they only airdrop foot units, unless modded again, and if you don't recon the area first, you lose your units if you try to drop them on an occupied tile.