I'll answer the others- Steakhouse.. nope, the $30 covers one serving. Though you probably won't want more. The porterhouse steak I had was bigger than the plate and about an inch and a half thick. The lobster tails are huge Main Lobsters, not the little tails you get in the main dinning room.
Lines on board- no, I did not observe any lines that were what I would consider to be long. IF you went to the buffet at the peak serving time there would be a line but they have 4 buffet lines so it was never bad. Some ships (like the Victory) do not have enough buffet service lines so there would get to be a long wait, but the Splendor does not have this issue. The ship is plenty big so it does not feel crowded. I don't think you will have an issue there.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013