I've never towed with a Murano, but, from a weight perspective, as you noted, you should be OK as far as the numbers go, but, you don't have the full story...you'll be a little light on power and you'll, of course, need a top notch brake controller because the Murano's brakes aren't really designed for much more than the vehicle's weight. Unfortunately, the Murano was not designed to tow an RV. It was designed more for small utility trailers or maybe a small boat or jet ski. It does not come with a 7 pin connector for a trailer with brakes (it only has a 4 pin so it provides lights, but, nothing more); no charging for the RV"s battery or power for the RV's brakes. Another issue is the tongue weight; the Murano's that I've been able to find information on specify a tongue weight of only 350 lbs. Your RV's tongue weight will be heavier ( most likely in the 400+ lb range) and you also have to consider the weight of the weight distribution hitch in that figure. The amount of tongue weight, from the RV and the hitch could well be closer to 500 lbs.
While looking at the "I can tow 3500 lbs and the trailer is only 3100 fully loaded" it would work, looking at the other specifications and limitations of the Murano tells a different story... I don't think that it would be wise to try that combination...sorry, I hate to tell someone that they shouldn't tow an RV, but, I don't think mechanically (your Murano will suffer for it) nor from a safety standpoint, would it be a wise idea.
My 2 cents, your mileage may vary...
2 Cats; J-Lo and Ragamuffin :R
2014 Thor Tuscany 40RX DP
2011 Ram 2500 Longhorn CTD HO
2011 Keystone Cougar 318SAB (now gone)
2008 FunFinder X 210WBS (Sadly gone)