I have a Yello Tang (about 3") in a 75 gallon. I know that he will get too big and I will have to move him to a bigger tank. I purchased a Potter's Angel and when I put him in the tank..my Tang went nuts chasing him, slapping him with his tail just like yours did. I turned the lights off for a complete night. The next day, the same thing until the Potter's bowed up on my Tang. Every since then, they are true buds. They play with each other, eat together and play follow the leader through the rocks. I also have a Bangaii Cardinal who likes to play with the Tang as well. Don't ask me why my fish are so weird but they are.
One piece of advice, when you are putting new fish in the tank, turn the lights off for at least 2 hours. If there is still aggression, move the rocks around a little bit so they have to reestablish territory. This typically eliminates aggression.
There is a good website out there Aquarium Fish: Tropical Freshwater Fish and Saltwater Fish for Home Aquariums
that has plenty of selection with minimum tank size requirements. You may want to check that site out for ideas on what you can house.
You can also do what I did and buy another tank and now you have 2. LOL.