Guns are honestly not that advanced tbh. Though maybe not a triggure based one like the one he suggested but a front loaded musket would fit in perfectly. Dynamite and fireworks are super simple as long as one knows how to make explosive powders.
I know gunpowder seems super complicated because of the smokeless nitroglycerin based powders we use today but the gunpowder that would likely be used would be blackpowder, a combination of sulfer, charcoal, and saltpeter (nitre). All of these are already in the game i believe and it wouldnt exactly take a scientist to mix a bunch of combinations of the three untill they figure out what combinations actually explode when lit. As long as they knew the 3 ingrediants that is.