It seems to me that this forge boon would be a good (maybe better) fit for grapple hooks rather than slingbow and fist weapons. Grapple hooks are a good offhand item for hunting and exploring, and you can use them to immobilize mobs like cuttletrunks and spotters. Having the bonus armor would help players who are getting up close and personal with danger survive counter attacks.
I’d suggest making it for fists and grapples. Slingbows have enough other boons to contend with that it doesn’t need more options.