Being laid up with a bad foot, I decided to work through more of the Amzi! Prolog tutorial. I really like the tutorial as it's clearly written and show how things operate under the hood. I read the lists chapter to see if I could learn techniques to better explain lists. Unfortunately, they are something that you'll either get or your won't. However, working through each of the exercises is like solving a bunch of mini-logic puzzles. I like that.
Here's my stab at various questions (they can be harder than they look, but as is often the case, a simpler answer is more likely to be correct).
split(X,List, Before, After)
N is N1 + 1.
That last one was tricky because the math must be done last to ensure the N1 variable is instantiated since math is not done logically in Prolog.