Not that I've done extensive testing, but I just went into two custom games, one with my talent page up to having five ranks in Runic Armour and one where I took off Runic Armour and had only two tiers of masteries. The value remained at 57 for both starts. With a 16% bonus, the number should have changed slightly had it any effect on his passive. Which is odd, because the effect in-game is described a shield and displays as shield health.
Spells and abilities have a slight difference in how they work. Abilities are anything that would be under Q, W, E & R. Spells are a subset of this, being abilities that deal their own set value of damage, are purely crowd control or are some type of buff or debuff. As an example, Garen's Q is not a spell, but it is an ability. Annie's Q is both a spell and an ability. Panteon's Q is also both a spell and an ability. What stat it scales off of doesn't determine whether it's a spell or an ability, but simply by how it functions. On-hit abilities are the most common non-spell abilities. As a side note: I'm not sure of any cases where something would be a spell but not an ability so as to need the distinction. Maybe someone else could chime in on that.
Intelligence raises your maximum CDR potential to 41/42/43/44/45%, but also grants you a free 1/2/3/4/5% CDR which every point invested. This means that you only need to ever buy 40% CDR with items but will have a maximum amount of 41/42/43/44/45% CDR.