The shrimp really isn't much in the way of bioload, so I'd say yes it's okay to add it. But, that having been said the two fish you have in there already bring things quite close to the limit (for fish) for a tank that size.
I'm content with not adding more fish. I'm changing 15% water once a week and going to start changing 5-10% twice a week to get the NO3 down(10+ppm) to add coral. So, I guess I'll feel comfortable adding the Skunk.
Add some macro. Watch the fish in the morning, they may be gasping. Add an air stone if they are. After you get some macro growing you may not need it. Ten and twelve gallon reefs have a real drop in dissolved oxygen levels at night when you are at the edge of your limit. With nanos, you don't keep an eye on the reef, you WATCH the reef.
