You touched several concepts, that have widely different understandings among people, based on the model of reality they subscribe to.
Regarding "being aware of others (souls) not being here alive on Earth now": our subconscious is / can be in contact with any other unit or gestalt of consciousness of the wider reality, not only from our physical reality, not only in this physical moment.
Our conscious side of our personality, unfortunately, is oblivious to our own subconscious and its capabilities. Occasionally, we get glimpses of those, and have all kinds of inexplicable experiences. I believe that's what explains your situation.
I believe that the widely quoted concept of "simultaneous time" is as wildly misunderstood, and misrationalized. It isn't that things happen simultaneously, or that physical time isn't linear. Not getting into more explanations, the way that you-here perceive the space and time of your dreams, is pretty much how a non-physical entity perceives our physical space and time.
Everything expressed here is what I believe. Keep that in mind when you read my post, as I kept it in mind when I wrote it. I don't parrot others. Most of my spiritual beliefs come from direct channeling guidance. I have no interest in arguing whose belief is right, and whose is wrong. I'm here just to express my opinions, and read about others'.