Eh, I just set it up so that unless the attack's target is "self," you can only use it on other pokémon. That's an enterprising user there, though. Points for outside-the-box thinking.
After you is a bit of an odd one, yeah, but I found struggle bug to be pretty intuitive, myself. The user is all creepy crawly and unsettling, and the other pokémon gets all freaked out and distracted by it, which reduces concentration and therefore special attack. The only odd thing about it is that it's not a contact move... when I first read the name and effect I assumed it would be the user climbing all over the target, giving them a light drubbing with its many limbs and generally being gross. I guess the idea is that the opponent is so revolted by the sight of the bug that they're actually physically damaged, but given that the base damage is actually higher than that of things like icicle spear, which is, you know, getting stabbed by a sharp ice thing, I threw some of that handy "bug energy" in there to justify it doing a bit more damage.
I don't honestly remember if I have super fang affected by damage caps at this point; I just have to decide what I want my policy to be on that as I work through the rewrite.
Some people don't like damage caps, and that's fine, really. As long as you're prepared to play the more aggressive style that not having caps engenders, there's no problem with it. I tend to use caps to help mitigate the potential for one person to really screw up their commands and have their opponent take advantage to the tune of 70% of their health, for example, and because I prefer the less aggressive style that works well with them.