I kinda got mastered on vibration problems. I've been experiencing problems for more than a year. This is what I'd do (in order if no improvement)
1) Check irregular wear on tires. If especially you're hearing grunting noise when about to come to a stop, your tires may be worn incorrectly due to a misalingment
2) If the humming noise increases as the speed increases (not just around 60), it might be your wheel bearings. Especially if you have more than 40K on your FX, it might be a problem
3) Wheels: Get your wheels road force balanced. If the above two are not the case, most likely you have a balance problem.
4) Check & increase your tire pressure a little. If you're running 30-32 psi cold, try 34 psi cold. Sometimes it solves the slight vibrations but don't expect anything major.
5) If nothing above works, go to the dealership and tell them to tighten the bolt on the steering wheel column. There's a bolt that increases/decreases the steering wheel tightness. Tightening half a tick can improve the vibration if the vibration is not tire/wheel related. This is what solved my issues. This isn't a major job. Just takes 15 mins.
6) If even that doesn't work, it's time to take a look at the drive shaft and/or steering wheel column.