I'm a long time collector of Kentucky rifles, and don't generally collect these types of rifles, though have had more than a few halfstocks in the past. With that said, value; If it were a run of the mill halfstock percussion rifle, in this condition with no original finish remaining, I'd say the value would be $350 to about $500.
George Schalk seems to be a notable maker of target rifles, so his name on the barrel will add to the value, but, most of any additional value will depend on the interior condition of the barrel. A pristine shinny bore, Great; but rust and pits add nothing to the value. Also, the false muzzle would add considerable if you have it, and reduce equally if its lost.
If you're going to use it as a shooter, I'd have it looked over by a black powder gunsmith to determine its condition as safe to shoot. Also, if you're going to use it as a shooter, I'd put some sort of finish on the stock. I don't know what Schalk would have used, but shouldn't be hard to determine.
One other possible issue as a shooter might be tearing patches while loading, without the false muzzle.
I think overall its a very nice looking rifle, and a bit of finish and fixing the broken trigger guard would make it look even better!
John