Your crown appears to be perfect and didn't need those little rat-tailed file grooves in the grooves, but, they shouldn't hurt at all.
If the patches are still shredding as before, the patches lack the required integrity. They are too weak, too thin or the bore is toast from using Pyrodex, prior to this?
I use the really thick denim, 12 ounce, which measures .030"av. in my dial calipers squeezed as hard as possible on the tines between finger and thumb. My Mitutoyou mic, measures it at .025 - compressed hard. This is my favourite patch for my 14 bore rifle with a .684" pure lead ball. It is difficult to load with the WW ball from the same mould, so when I want to shoot hard lead, I use a .677" mould which throws .675" WW balls. they load beautifully with the heavy patch and do not burn out - AT ALL. I can actually use the same patch for a 5 shot group, picking it up, re-lubing it and shooting again and again.
What this mean- is something is wrong with your patch material - or barrel.