Not seeing any significant rust on the FD, and Shimano FD's are pretty rust-resistant.
What happens when you undo the cable? the FD should return to the lowest position, and you should be able to manipulate it with your hands at this point.
When the cable is undone, you can also see if there is any resistance/lack of movement if you use the shifters.
One other thing, it looks like you spend a lot of time in the middle ring, sort of hard to tell from the angle of the photo, but the chainring looks a little pointy and you may want to consider replacing it (the middle ring) at some point.