Regarding number 1, the gunpowder (smokeless powder) itself isn't go to give you any highs, though.
If it contains nitroglycerin then, so the theory goes, it relaxes the veins and allows other drugs to get you high quicker (as in Brown-brown). But on its own it's not going to do much else.
Other ingredients could potentially be toxic, but in all likelihood the granules (which are much larger than fine cocaine powder, for example) would remain insoluble, mucus would form around them in the lungs and you'd cough it up as phlegm some time later.
Please feel free to add this side-effect if you wish, perhaps followed by the player character audibly saying "What the **** was I thinking" inbetween coughing & spluttering
charlie2good
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