Apparently I forgot the existence of this thread so sorry for a slight necro, but I think I might provide with some useful comparison screens in case someone in the future decides to search this forum with a keyword "Field of View".
So first a few notifications:
1) I was initially 100% wrong since, wider resolutions
DO in fact automatically increase the horizontal field of view in game.
Comparison (first is 4:3 resolution, second is 16:9 resolution, both using default vertical fov of 75):


2) Different fov parameter values have no effect on in-game cutscenes. However, wider resolutions do have an effect in overall visibility.
3) Outside of cutscenes (aka in normal gameplay) a -fov increase is out of the question, since the fish-eye effect grows too strong. On the other hand, smaller fovs result in less situational awareness:
Comparison 2 (Fov parameters of 30, 60 and 90 all using a 16:9 resolution)



4) Conclusion? Well this has been a waste of time all along. My arrogant intuition led me to believe that a game this old can't possibly have a dynamically changing horizontal fov with wider resolutions. But I'm glad I was wrong this time. Saves people a lot of headache. The original Fov value is good for most purposes, so I don't recommend to lower it down as much as the HLP wiki suggests. That results in way too much zoom. A decrease of 0.05 to 0.15 should be more than enough.
BTW this following website is very good for getting solid widescreen experiences for older games. You should definitely check what else it contains:
http://www.wsgf.org/dr/freespace-2EDIT: Forgot a detail.