The Mag 7 will work with the EV 180. You may not get the maximum performance that the skimmer is capable of, but I think it would be sufficient for a your tank. I also think that since you have the Mag 7 already, it would be hard to warrant spending the $$ for a new pump to run the skimmer. You can always upgrade it later if you see the need.
The protein skimmer basically generates lots of tiny bubbles that attract the dissolved organic molecules in the water. The DOC
's cling to the microbubbles and are carried up into the collection cup in the form of a dry foam. That's the short version anyway. If you have ever been to the beach and seen the waves lapping up on the shore with a layer of foam on top, you have seen natures version of the skimmer at work.