Wideness is a sign of the extension of consciousness out of the ordinary limits, whiteness of the wideness means that it is the pure consciousness one is feeling, unless it is white light or luminous light which indicates the Mother's consciousness there or some influence of it. The subtle barrier you felt must have been the same thing that prevents your ascent from the heart and from it your going beyond into the regions above. There is always a sort of a lid there and it is only when that is opened or disappears that one can go freely above. One can be aware of "unseen wideness" but one is not a self there until that is done.
The wideness of light you saw was the wideness of the true consciousness liberated from the narrow limits of the human mind, human vital, human body consciousness. It is true that the mind is narrow, not only yours, but all human minds even the most developed, compared with the wideness of the true consciousness which has no limits. It is precisely this wideness which will come by the sadhana and which these processes are preparing.
The emptiness and wideness in the brain is a very good sign. It is a condition for the opening horizontally into the cosmic consciousness and upward into the Self and higher spiritual Mind above the head.
This wide consciousness not dependent on the body or limited by it is what is called in yoga the Atman or Self. You are only having the first glimpses of it, but later on it becomes normal and one feels that one was always this Atman infinite and immortal.