So really, he's not THAT screwed once the Spiders are all dead.

I mean, he just can't use his chains. So couldn't he just learn to Conjur something else?

And even if he can't, he can still use his other powers half-assed.

I mean, that's probably not enough to allow him to keep up during a shounen plot, but that probably won't happen till the end of the series anyway. And he'll probably still be strong enough to earn a living anyway.