Hi,
I really believe that you have a mighty fine short range hunting rifle.
It really burns my cookies when I see some jack ass drilling holes all over these muzzleloading barrels to put a stupid scope on it.
And I'm 65+ :stir:
And I can still see......a bit.
To repair your tang, just flatten out the bend a bit, carefully inlet it, put a plug in the old hole ( in the wood ), drill a new hole for the screw.
Now you have a fine lookin' gun especially since you replaced the under rib.
All the best with a fine hog & deer gun!
Fred