There are many very serious things blood in the stool could be, and none of which can be solved based on descriptions over the internet. you need to find the money to take this dog to the vet or take him and surrender him to a rescue that can properly care for him.
if you cannot afford $100 at the vets right now, you really can't afford to have him.
if you cannot afford $100 at the vets right now, you really can't afford to have him.