I've been running a very similar deck for some time now - it's my favorite deck and the only one I regularly play. If I can make 2 suggestions:
-2 Displacement Wave
-1 Advanced Stitchwing
+1
Kozilek's Return+2
LanguishKozilek's Return is a no-brainer with Emerge. I've never had trouble getting it into the graveyard, and you run 5 more ways to put it in the graveyard than I do. It's definitely a better card than the 3rd Advanced Stitchwing - I've found that Advanced Stitchwing is almost always discard fodder for Haunted Dead anyway, and I never really want more than one to show up in a game (although I run two).
Languish is a better sweeper than Displacement Wave; your emerge creatures survive it, and your zombies don't care about dying to it because they'll be back. Given your discard sub-theme, you want to empty their hand, not put things back in it. And you already have Compelling Deterrence for things that survive Languish.
I don't run Imprisoned in the Moon, but I do run 3 Compelling Deterrence - it helps the discard theme quite a bit, and it also deals with Planeswalkers and Tutelages. I also run 3x
Vexing Scuttler instead of the Drownyard Behemoths so I can get Compelling Deterrence or Whispers back. I haven't lost to Superfriends in quite some time - Compelling Deterrence gets the job done. I do like the Drownyard Behemoth here, but I've found recycling my own spells is more useful. I guess Possessed Skaab serves that purpose for you though - how has that worked out? I avoided it because I rarely want to spend 5 mana on a creature, and for the same 5 mana I can cast Vexing Scuttler and either Whispers, Compelling Deterrence, or Take Inventory in the same turn. But I haven't actually experimented with the Skaab and I'm interested in your experience.
Also, if you can find a way to put
Liliana, the Last Hope in, you won't be disappointed. While I've won a few games with her ultimate, the real use is getting an emerge creature back from the graveyard.