Unfortunately the GTX 745 is a very low spec Graphics Card. That's about as much as you can expect to get of it playing FFXIV.

The CPU in your computer will run the game very well though.

To get the performance you were hoping for you would need a GTX 750ti/R7 260 (roughly $100 Video Card)

Switching to a lower resolution would probably be your best bet to get better frames with the GTX 745, since it has such a low pixel rate it's not a matter of turning down graphics so much as lowering the number of pixels it has to render (lower resolution = lower pixel count/detail)