Nothing about MLC is normal, but yes this kind of disordered and nonsensical behavior is the norm. Honestly as hard as it is you have to detach, not engage, offer no observations, no commentary. If you have to be around him just acknowledge things with no commitment or emotion, no matter how hard it is don't offer help, advice or observations. Anything and everything you do will simply be turned around or cause some kind of reaction, trust me. And whatever you suggest, no matter how sensical, will suddenly be the wrong thing (sky is not up, etc).
Try to keep reminding yourself that due to a significant psychological event this is no longer the person you know, and no normal emotional or logical rules apply. You are around a person who is internally fractured and spewing out negative emotions they can not contain. So think of it as being around an out of control set of spinning blades, how will getting near that or trying to touch any of it be good for you?