If I have Half-Breed and one other Race card, is my other half human?

You get the "all the advantages, none of the disadvantages" benefit of Half-Breed for your other Race, but you can't use Human-only items or claim bonuses against monsters that have trouble fighting Humans. (As a practical matter, there are very few of these, so this doesn't come up that often.) Note that this answer is specific to Race and Half-Breed.