I can't just spawn an explosion, I have to spawn a missile which explodes instantly to get the effect. The explosion radius/strength of that missile can't be modified dynamically, it's always whatever it's set to for that missile. This is a limitation in the core of the game engine (the definition of things cannot be changed during the game, only during start-up)
This mod was a silly idea implemented quickly and I doubt I will spend significant time upgrading it so feel free to make your own version with the features you think should be in it!