Answers to your questions... Yes, yes, probably best. Should if impact ready. Because Ducati Corp are idiots.
Yes that linked dual sprocket is the correct size and should work. However because the rear nut is usually torqued to around 170 lbs/Ft so if this tool isn't rated for impact use, I wouldn't bother.
I ponied up and got individual 55 mm ($45) and 30 mm ($16) impact sockets (front isn't really necessary impact). With my impact gun, the rear nut came off no sweat.
I'll second impact sockets. I just did a sprocket change on my S2R and ordered an impact off of Amazon. It came off without a sweat and is much easier than trying to use a breaker bar while trying to keep the wheel from turning.