<StateReligion> I think requires you to have that religion as your state one to build it (What needs to be put there I don't exactly know).
<bCenterInCity> is a variable that the palace uses to tell the game to always place it in the center of the city when drawing it, so using it for anything else might cause issues.
<iMinAreaSize> is a variable that tells the game the minimum number of tiles squared that the building needs (for those extra large ones)
<iMinLatitude> and <iMaxLatitude> are used for things like restricting buildings to the tropics (like a rain forest preserve. Hey, it's possible) or elsewhere (like a skating rink being restricted to the artic). 0 denotes the equator, while 90 functions for BOTH poles. So, if you'd like, you'd just mess around with the numbers, and set them between 0 and 90. It will mirror it for both poles.
<iNukeExplosionRand> is intended for nuclear power plants, which would have a 0 to 100% chance of a nuclear meltdown (Hint: place it between 0 to 100).
<SpecialistExtraCommerces> should have the first as gold and the second as science. <CommerceHappinesses> is the same
<YieldChanges> and <YieldModifiers> should have the third option as commerce
I'm not editing it as I can't play the game yet, but the stuff I've said should be right, as far as I know. So, if you find it helpful, go ahead and change them.