Hi!
Welcome to the modding community!
I only took a quick look at your code, but it looks to me like there is a lot missing from the weapon entry. I guess for a grenade-type weapon (that's what it is, right?) that might be ok, I'm not sure.
Any ways, one thing that did stick out was the lack of any hand objects. In the extra sprites, you need to provide a picture that tells the game what a soldier holding this weapon will look like. They're called "HANDOBS" in the code, if I remember well. Try to provide one, maybe flesh out the definition a bit, and if it doesn't work, someone here can probably fix it!