You want to be able to rotate it on Mouse X input and adjust the radius on Mouse Y input? You can just promote the other pin of the multiplication node (which has one of it’s pins connected to the forward vector) into a variable and adjust it’s value accordingly.
I’m not talking about the existing multiplication node in your blueprint code though. It’s the new one that I described previously. You can determine how far the sphere should be while rotating by adjusting the value that we’ll use to multiply the forward vector of the actor we’re rotating it around. Then again, place the sphere on that location either by using the world location or the relative location.
In that case, I think it’d be better to add a spring arm component as the parent of your sphere. Once that’s done, you can simply rotate it on Mouse X input and adjust it’s length on Mouse Y input.