It's getting Impossible to even give them water at this point, they nearly killed me last time. Idk if this is possible but it doesnt hurt to request. Sorry if I set this up wrong, I just joined.
There is a ring in-game that makes it so that slimes can't hurt you. You get it from the Adventurer's Guild as the reward for killing 1000 slimes. As it is, why not just edit this item into your save or use one of the trainers that can spawn items?