Difficult to say but my own experience with introducing another tang has been bad. Though in my case I tried to introduce a bigger yellow tang with a small purple tang in the tank.
Just saw your post and it strikes a chord as I have the exact same experience when I started out last year. Almost give up but I stopped trying to put fish in. Put in a few easier corals and I let my tank run fish less for 1 month plus.
Have fun with your fish!