i left the fov standard, as 100 in all resolutions
however, this doesn't change much as most people dont even play with stock FOV, i myself play at 130, most people choose something around 110 or 120
the game's FOV does not auto-adjust with resolution, but just reduces distortion
say you use FOV 130 at 1024x768, you'll see a good deal of distortion, much like looking through a wide-angle camera lens
FOV 130 at 1440x900 is just as wide, you see just as much, but due to the extra horizontal screen space, the distortion isn't as noticeable
Yes, that's the way FOV works, but having a widescreen monitor is all about being able to see more horizontally, therefore you don't want to use the same FOV, but a larger one to be able to see more.
I'd recommend you setting the FOV to its default of 100 for 4:3, then using the FOV calc i linked to previously to take screenshots of 16:10 and 16:9 in the correct FOV in relation to the 4:3 AR.
Here i'll do it for you
4:3 = FOV 100
16:10 = FOV 110
16:9 = FOV 115