Recommend you use 0 Pyrodex. It contains chlorates - technically perchlorates which are still chlorates. Chlorates are what made old time primer residue corrosive.
Only use black powder only - but if you have to use a phony powder, use T-7. Start about 30gr. and go up from there. I'd suggest that 2 balls, only the last one loaded with a patch and 50 or 60gr. 3F might be a proof load of sorts. I use a .350" ball in my .36, however I'd much rather use a .355" or .360" ball in that barrel. I use a .020" up to .0235" patch, all giving easy loading. The smaller the ball, the more easily they conform/swage into the bore, with the patch.
What powder charge does the barrel maker suggest as a top or max. load? I have no idea what a max load would be. I've shot up to 70gr. 3f in a .36- 7/8" bl. with no problems other that there was slightly more fouling that cleaned with the next load pushed down.
A smoothly radiused crown makes loading easier and eliminates any tearing of the patch. A thick patch eliminates burning - burning is caused by powder gas and flame blow by. Eliminate the blow, by using a tighter patch and problems solved.