I don't recollect your saying what the twist of the rifling is. The slower the twist the more powder you can accurately use. Emphasis on accurately. Let your rifle tell you what it wants, don't try to make the gun bend to your desires. It ain't gonna work.
As far as your patches go, yeah, it does look kinda blown out. If you want to cure that, it is very simple. Get yourself some 24 gauge, pre-lubed cushion wads. Load powder, cushion wad and PRB. The wad will wipe and lube the bore, it will prevent the patch from being burnt out, and you will pick up an additional 50+ fps. Sounds like a win-win-win to me.
John (Bigsmoke)