As far as I know the pistol shrimp is invertebrate safe. They will be fine with cleaners and other shrimp. There is a good chance that your yellow watchman will strike up a relationship. I will have the exact same pair in my 75g setup.
I live in MD also and I was wondering where you buy your saltwater equipment and livestock? Im having a bit of trouble finding a reliable saltwater dealer around here. I would have PMd you, but for some reason, I cant?
Thanks.
Mark