Breithorn is very easy. I think it is more climbed than Mt. Fuji due to its accessibility near the Klein Matterhorn. Even though you say you are a novice, give Pollux a try on the same day as Breithorn. If you get the first tram in the morning you can make the Breithorn and Pollux in the same day and back to the tram and Zermatt...but it is more fun to stay at the huts. If you do Pollux and Breithorn in one day, I would definitely try Pollux FIRST. The route does narrow with chains, and the guides FIGHT and do YELL at you like they own the place....the earlier you are there, the more you are out of their way for the unpleasantries. But, on the other hand the fighting is part of the European experience.
Most people climb the Dufourspitze/Monte Rosa from the Monte Rosa hut....not from the Margherita hut.....you would probably have to find a way down to the route and then back up the standard route.
The Margherita hut is the highest in Europe...and you can see the Dufourspitze/Monte Rosa directly across from it....it would be cool to be in there.
You can climb the Dufourspitze/Monte Rosa from the Monte Rosa hut getting an alpine start (3:00a.m.ish) and back to the train and back to Zermatt all in the same day.