Is it possible to use the patent to make the E-cat?
Yes. To make a working model - to early to tell.
You would have to license it through the owner. If he is not interested in licensing it...nope.
There is a reason the electric company is named Consolidated Edison and Westinghouse. Those are the guys with the patents.
IMO, yes. This US patent gives far more details than Rossi's earlier Italian patent. There are several items in the patent that had not previously been divulged....specifically the inclusion of metallic lithium powder (in addition to the lithium aluminum hydride) in the fuel mix, and a composition formula giving rough amounts of nickel, lithium powder, and LiAlH4 needed.