That is very strange that it has the wrong cover on it. It would use whatever cover you uploaded for that book. Maybe try reloading the cover? Did you name the book test in your D2D meta? I used to do that to keep them separate in the list. I have to keep two separate books for each book on D2D. It uses the title in the metadata as the title in the file. I have to be very careful to not accidentally release the one I'm using as a meat grinder, but I've gotten used to checking on the book list for "released" and "draft" and making sure I use the right one.
You have to go all the way through the process including pricing and just NOT publish it to get the file. I do it for epubs though, I've never tried a mobi. But I do details, layout, preview, and then when it takes me to the publish window, I close D2D, go back in and grab the file from the book page.