The 6 volt speed control should be fine with the 12 volt motor. And an inline fuse is a good idea. The change from a 14 amp to a 10 amp fuse sounds about right as well. But.. the wire you have is rated at 14 amp so there is no real need to change if you don't want to. The 10 amp fuse might, just might offer a bit of protection to the new motor. The rest of the system will be just fine if the wire and switch are in good shape.


Steve H