Thanks for the support!
As for some suggestions, perhaps it could be interesting to give the crabs a small animation where they spread their claws before they lunge? I did think it could be frustrating to not know when they're going to jump, unless that's part of their charm.
They have some sound cues in addition to a limited range, but I think it's best to keep players on their toes without a clear indicator. The main thing is just staying away from where they're facing, there's a randomized cone of about 20-30 degrees where they'll lunge if they're lined up at you.
For weapons someone mentioned a radiation gun, I like that idea, perhaps it could be some kind of short range weapon that does that blast thing with nuclear explosions where everything gets incinerated by the heat and it does that puff of smoke on everything (I don't know if that's really clear though, explaining is not my forte)
Will experiment with this concept, cheers!