As awesome as FE is (to which I am a highly devout fan), there is little in the ways of inspiration from that series in this. It's mostly from Dark Souls, Pathfinder, and a (small) snippet of Skyrim. Most of the answers to your questions, [b]especially[/b] exact formulas of Parameter influence over other stats, won't be explained, in order to avoid game-breaking and min-maxing. Not that I distrust people here, but it's easier to be sure if the power to break the game is never revealed. Battle calculations like hitting, acting multiple times, and other things will be explained though, but in due time, as they are not all 100% complete. The EXP formula is pretty simple. I'll put up a chart for it, but the formula is:

Exp to next level = (10*(1.15^(LEVEL-1))) Rounded down to the nearest whole number