Yes, he needs the fluids...this is the Ivermectin and the stress on his kidneys, and he needs the daily sub-q fluids. I hope you were able to get him to the vet again for the fluids, and so that you can learn to do them at home daily...If you did get him to the vet for the fluids, when he gets home they normally perk up a bit after getting the fluids, at that point while he's feeling a bit better, then try to get some nutrition in him. He's weak, dehydrated, and not feeling well, but that's to be expected. This is the normal course for Ivermectin poisoning, I know we've seen it before and you haven't, but I do not at all suggest giving up on him or thinking of euthanizing him at this point, he needs the daily fluids and then nutrition...honestly, this is the normal progression of recovery from the Ivermectin.