Steve-

What really sucks here is that at this point I don't want that rifle any LESS than I did yesterday!

The conversion from muzzle-loader wouldn't surprise me one bit.
I'm not sure where anyone stocks 14-bore cases, but I think you can find some here in the states -- and you don't need paper.
I've run some pretty massive charges of black powder in plastic cases with no trouble -- but you can only do it once per case.

Have Rocky Mountain Cartridge knock you a box of brass cases out for that thing - or just whittle a couple out on the lathe...

Did you note what the rate of twist is for this rifle anywhere..?

Cheers
Tinker