I think you could be firmer than that, biting you to the point of bleeding should never happen and i can certainly understand your frustration!

Do you have the option to give him a time out? Put him in an area where he can't hurt himself but there are no toys or other diversions for him to play with.

If he bites you so hard he should be put there for a few moments. He might whine or bark but only let him out after he's been quiet for a few seconds to break the link between barking and being let go.

What you're doing now is fine for when he nibbles or accidentally bites your hand when you're playing but I think for the bleeding you need to escalate the consequences of the behavior.