Benjen is probably Coldhands, who still can potentially come in this season, and there's a chance to with Bran's involvement with both the Three-Eyed Crow and the Night King.
I think the Tower of Joy is best explained in the books, as in, it will be, however I think the show is absolutely going to follow R+L=J, and use the scene as a transitioning point towards the revival of Jon Snow and the reveal of the truth. At that point, Jon will be legitimized, as either Stark or Targaryen, and either plan to retake Winterfell, the Iron Throne, or fight the White Walkers. Or multiple. There's a picture leaked of the actor wearing Stark armor, and all groomed up, and the small teaser at the end of the trailer shows Jon Snow and Davos Seaworth with Jon's sword. My guess is Mel will figure it all out, try to resurrect him, and will, and Jon will be fulfilled as Azor Ahai, and officially made the subject of A Song of Ice and Fire.
