WOW! Thanks for taking the time to lay this out like this. It’s a great help! More then you know.
First off, I just want to have this be an option for the player to use. A lot of users claim that they don’t get motion sickness like most of us, so I just want to let them be able to decide between some controls. 
However, using the rotation method I setup is actually quite comfortable, and I know it would be a lot better if I could get this to rotate right. So at least we know why I’m trying to set this up.
I have been trying this out, but I haven’t had any luck. I broke this down the best I could understand it.
1: The first thing you’re doing is setting the position of your holster and mid to your camera. Since I didn’t need to do that I skipped over it. I’m just trying to rotate the VROrigin on the Z at the cameras XY location. Although I tried to SetRelativeLocation of the VROrigin to the camera, but that was instant motion sickness, and it STILL didn’t rotate at my feet… :S Not sure why. So this got skipped. As I figured I didn’t need it, and it didn’t work out for me.
2: I see you’re basically just getting the degrees of the two vectors here from each other, so I didn’t use this either since I don’t actually need to do this for what I’m trying to achieve.
3: I actually don’t need this either, because I’ll be rotating my player in increments to prevent motion sickness, and I have a scale Delta plugged into a float for smoothness if I needed it. HOWEVER… I did discover you’re rotating relatively, and I was adding local. So I did learn a little bit on that. tips hat
But I’m unfortunately still unable to figure this out, and I’m starting to think it may be a bug? Perhaps an issue with the camera maybe? When I look down and rotate, it should be rotating at my feet. If I AddRelativeRotation to the Camera, nothing happens. If I AddRelativeRotation to the VROrigin, it rotates, but not at the camera’s location. Sigh. I think yours works well because you’re setting locations to the camera and rotating them, but when you try to actually rotate the camera, it doesn’t work, nothing happens.
Uhgf…