On second viewing, this is definitely what they were going for. It wasn't executed perfectly but, I shall dramatize it for you:
"I'm Kylo on the bridge, there's light side stuff in me but you can't see it cause of my super awesome Vader cosplay i'm so dark DARK SIDE DARK SIDE!"
"BEN! Take off your goddamn helmet!"
*takes helmet off" "omg Dad now you can see all the light side bits in me it's tearing me apart" >_<
(This is bluntly symbolized by the light of the dying star shining through the window and illuminating Ben's maskless face while the rest of him is dark).
"But Dad, u can help me?"
"Sure whatever just let go of the fucking lightsaber"
(All light is drained from the star; Ben's face is left in shadow. Now he knows that he is truly Kylo Ren, he has made his choice and embraced the dark side. He no longer needs the mask to hide his uncertainty and susceptibility to the light).
(HAN SOLO IS KILL).
"Now I am UberDark Kylo Ren, nothing will stand in my way for REAL this time, and I won't be needing to hide anymore."
--
Thing is of course, making that choice is nothing without the discipline it demands. His emotions still absolutely rule him and he's not channeling his rage or hatred, just letting them drive and, as we all know, leaving him with a bunch of saber wounds and one last failure.