I would not try to introduce them anymore. When I introduced my cat to my new husband's great dane, I just had them in the same area, nothing in your face about it.
My cat hissed a lot and hated the dog (a great dane is a lot for a cat to get used to), but eventually they tolerated each other and the great dane learned that the cat was not a plaything.
By the way, a little scratch will not hurt your dog and it'll set up a pecking order (cats usually are at the top). If you try to prevent that, they'll never come to an agreement and they'll never get used to each other.
Ha ha, that reminds me my brother's great dane being introduced to our cat. Cat hissed and growled while the dog cowered in a corner :) Funniest thing I ever saw, a 75 lbs Great Dane in a corner but she was taught to be gentle to other animals. Over time our cat simply learned to ignore the dog and visiting was enjoyable for everyone.