I see you still have 150/40 as inner/outer radius of the ApplyDamage-node in that last picture. Try setting them to something like 500/1000. Make sure the outer radius is larger than the inner radius.
As for the channels: I don’t know. It doesn’t look like you can disable it completely. So all you can do is to create a new channel and set it to ignore by default, if you want to.
About the radial impulse: I wrote something about it in the comment above. If you want to use it, you have to do a “manual” query followed by a loop.
edit: You say the impulse affects only the guy that was hit? That’s very strange, because the way you have set it up, it should actually be applied to the rocket itself…