Sourcing the Components for Solid Rocket Fuel

The search began where every search begins. Google.
Searching for each of the 3 primary ingredients Potassium Nitrate (KNO3), Charcoal and Sulphur, I found that Charcoal is very easy to make. Willow is the wood of choice but pine works well too. Potassium Nitrate is a common stump remover but also works as a fertilizer.
Sulphur is where things get a little complicated. To start there are a variety of forms of sulphur and its -ites and -ates but I need pure elemental sulphur of which there are a variety of states but that can go on and on. What I know is that I need to find a source of crystalline sulphur or a sulphur containing product that I can purify without having to melt the sulphur (MP= 239.4F=115.2C) (changes the state/flavor to something undesirable).

With a vague idea of what I was looking for I hit the stores first to make charcoal because its the easiest. I grabbed a paint can, put a hole in the top, loaded it with pine shims, sealed it up and cooked it for about 2 hours.

The shims are convent since they are fairly consistent in their shape and cook evenly.

Next I went on the chemical component hunt.

Turns out Spectracide Stump remover says it is 100% Potassium Nitrate but I think there is some sort of binder in it that keeps it powdery so I will recrystallize it to purify it. I tried every big box store out there before I was able to find the stump remover it was only in one place that I would rather not advertize for but their name starts with an "L" and ends with an "owes". Anyway that was the only chain type store that kept it in stock.

So I attacked the KNO3 first by dissolving ~450 grams in 1L of boiling distilled water. KNO3 has a very high solubility/temperature correlation. I simmered it until I saw crystals start to crash out. Poured the solution into a Pyrex glass baking dish. Then I slowly cooled it in an oven over the course of a few hours. Next it went up on top of the refrigerator for a week or so and very large crystals formed. I filtered these out and rinsed them with ice water. Resulting in a VERY high purity product (>99% for sure).

Next I found this garden sulfur. The ingredients are 90% elemental sulfur 10% "inert ingredients". Which of course are proprietary on the MSDS. Considering the fact that sulfur is hydrophobic and insoluble in water apart from its tendency to form clumps in powder form, I figure the inert ingredients have to be some sort of binder that readily absorbs water giving their product the "wettable" property. This could be a number of things the most likely candidates are CaCO3 calcium carbonate or chalk OR Bentonite Clay which is basically kitty litter. I am fairly sure it is the clay so I have been researching how to separate the two but it is more difficult than I thought.