bill1949,
The horn will work fine wiring it the way you want...through the steering column sans relay.
Be sure to fuse the line, or supply side of the horn. The relay made the horn more energetic, and the fact that the horn button on the steering wheel was only switching the small relay coil made it a little safer...but it's fine the way you intend on doing it. It was done in millions of cars for many years that way.
You are correct, if you double the voltage, you half the amperage a device will draw. Your horn is going to be on steroids on 12 volts...be prepared.
Stuart
