I had the same problem when I installed my 50" KC bar, it almost sounded like a dremel tool inside the cab going down the highway. I'm using a SoCal Supertrucks mount which has similar placement to your mount putting the center of the bar close to the windshield/cab centerline. While this looks cool, it also creates a high vortex area which creates a lot of noise.
I know, not a Ram, but the physics remains the same.
Instead of foam try this, to isolate the fins buy a couple feet of 3/8" rubber fuel hose. Cut it into 3" sections and then take each of those section and slice it length wise into quarters (so you have four 3" strips)
Now starting at one end of the bar insert a strip inbetween the fins (skip every other fin and you shouldn't need any adhesive), then go down 10-12" and insert more strips except do the opposite fins of the previous. Alternate and do this across the back of the light bar. This will keep the fins from resonating.
Also, from your pics, it looks like you have the bar aimed upwards, that will make the noise a lot worse. Aim it to that it is parallel to the ground to start and then start adjusting it upwards in small increments until you get it high enough with minimal noise.
I can snap some pics of mine up close if you'd like.
You're never going to get rid of all the wind noise, but you can minimize it.