There is absolutely a barrier between dreaming/non-dreaming. Not sure if anyone can refute that. Reality Checks work because you can decompose limits in dreams. You can not decompose material limits in non-dreams. So my humble advice to Unimatrix is to keep working on reality checks. And do cvdmedhen's style of contemplation/meditation on RCs mentioned in day 2. But keep trusting in your own contemplation method to assess dream/reality. My advise to myself and to you is to think of a reality check that does work in dreams. And set intent to remember it always.

Breathing through nose doesn't work that much for me, it has become a habit. And i have seen atleast one dream report (wakingnomad) who claimed a dream in which even that reality check failed him. So for me it is still a goal to think of a RC that works. And i believe the power of RC is slightly underestimated.