Edit it to what?
I've never really understood what FOV i have in game, how can i check? i'm using 1920x1080 with the resolution changer.
If you haven't changed your Field of View to anything beyond 75, then you don't need to change it but trust me, you should look into it since you're using a widescreen monitor. FPS Optimizer can change Field of View. Let me try to explain WHAT it is, though:
It's not particularly correct to say so, but you COULD think of FOV as "zoom". Have you ever noticed that when you play most games at a higher resolution, you will be able to see "more" of the screen? For example, Oblivion accurately calculates Field of View so if you play at, say, 600x800, you will feel as if you have your cheek against the blade of your sword (imagine that your head pushed forward on your shoulders). Now, increasing your field of view would be the equivalent of moving your head BACK on your shoulders.
So, in morrowind, what this amounts to is that with a FOV at 75, looking straight forward with, let's say, a Daedric Dai Katana drawn, you will see the middle part of the blade, but with a FOV of around 91 you will see more of the Katana and the hilt, plus your hands gripping the hilt, something you could only normally see at FOV 75 by looking down towards the ground. This is more realistic, because if you were to hold a sword in the same position as your character does in game, you would be able to see your hands holding the hilt in your peripheral vision. You can't get a MOST realistic field of view in morrowind without distortion, however, because our monitors are not the same aspect ratio as our eyes.
I hope that made some kind of sense. Haha.
EDIT: By the way, the reason you need to change the FOV in Phal's shader is because otherwise the sun will draw to the screen in a really freaking weird way, so that if you look up the sun will literally move down, sometimes below the horizon if it's late enough in the day which is pretty crazy looking, as if the time of day is changing depending on the angle you are looking.