Good post Lord, but I'll simplify for you my friend.
Yes, you need an F-spaced pickup for that paticular guitar. F-spacing (as DiMarzio calls it) or TremBucker spacing (as Seymour Duncan calls it) are actually made for two reasons.
1. any guitar that uses a 25 1/2" scale (ala Fender) has a wider string spacing at the bridge than a guitar that uses a 24 3/4" scale(ala Gibson) regardless of wether or not it has a trem.
2. 24 3/4" scale guitars that use a floyd have a wider string spacing as well, as that is just the way the floyd was designed. You can't get a floyd in different spacings.
Your paticular Ibanez uses a 25 1/2" scale, so definately get an f-spaced replacement for the bridge position p/u. And also, DiMarzio is OEM on a bunch of ibanez guitars, and in fact the IBZ INF2 pickup that comes stock on that paticular model is made by DiMarzio and it is f-spaced.
Hope that clears it up for you