Good you stopped the milk, that can cause diarrhea cats don't tolerate milk well. But I'm thinking with the diarrhea and occasional blood that he has worms, very common in kittens. Take him to a Vet and get dewormed don't buy that over the counter junk, it's not effective plus it can make kittens very ill.
As for the sneezing, this needs to be treated too it's common especially if kitty came from a cattery. Get it nipped in the bud before it turns bacterial and spreads to the lungs. So basically see a Vet ASAP.
I'm glad that you got a kitty. Sorry it's having trouble.
I agree entirely with Opus.
I hope he feels much better soonly. I know goiing to the vet is a hardship for you but you'll find a way.