If you aren't getting good accuracy with a substitute powder like Triple Seven, how about using Black Powder instead? YOu can't possible read this forum for very long before you find out that virtually everyone here prefers using Black Powder. There is a reason for this. And, notice that almost everyone who has a gun like yours is using LESS powder, and not more!
My God, man you are shooting the equivalent of a .22 rimfire. 20 grains should be enough, and will give you good accuracy. Your current loading is 50% higher that that recommended load, using substitute powders. From the experiences I have had, talking to other shooters who have those small caliber rifles, over the years, and from reading comments by other members here, things have not changed a bit: They all like about 20 grain charges of FFFg powder for a nice, accurate load. For the .36, most rifles like a 30 grain charge.
Don't over load these small caliber guns. Even with 20 grains of FFFg powder, that little ball is buzzing out the barrel at a very fast clip. There is so much metal in the barrels around these small bores that its next to impossible to ruin the barrel, or rupture them, but you aren't doing a lot of nice to that flash channel and nipple. Save the powder and get in more shots per Expensive can of powder. The gun can serve you well for many generations of shooters.