Here is my second part. I've trimmed (marked with dots . . .) the text to narrow down what I'm commenting about.
We seem to have several concepts here, could we try to clarify these concepts?
1. Pretas - they are beings of their own. Pretas are somehow born (?) and they don't seem to be emotionally stuck in any way, and are living in a world of their own. In a non-physical Preta world or just a world different from our physical world?
They are emotionally stuck indeed, just as most human beings are emotionally stuck. Yes, they are living in a world of their own but it overlaps with our world, just as the animal world does. Hence my example. According to your very own definition of "physical," the preta's live in their own physical world.
2. "Thought-bodies" - they are the consciousnesses residing in the max 49 days Bardo, right? Once physically living, but now they have transitioned to the Bardo after death.
Into the bardo of becoming, yes.
3. Spirits - hmmm... You made things very difficult for me to understand. Spirits are conscious beings. They are beings similar to Pretas or physical humans, right? But Spirits are very different from Pretas? At the same time a Spirit is also equivalent to the physical (dead?) body, which a once living human left behind when the physically living human died and had its consciousness enter the Bardo?
You're confusing yourself with your own words, here. The term "spirits" is really not useful when discussing the bardo, thought-bodies in the bardo, or living pretas.
4. "Ghosts" - the same as Spirits?
These are two different words each with about a dozen different meanings.
So what you say is that I am seeing Spirits, because they act and look exactly as their once physically living counterparts? Most non-physical dead persons I've met in some kind of non-physical appearance have been dead for several decades. Are those (for decades) "dead persons", the same as Spirits?
They're definitely not people passing through the bardo. And if they don't look remotely like pretas they're probably not pretas either.
Some mediums claim that "dead persons" which the medium can see, sometimes looks younger (similar to the once living person, but younger) than they were when they died. Are these younger looking entities also to be regarded as Spirits?
In my communications with "spirits" yes many of them look younger and are wearing certain clothings and so forth. Pretas don't look that way. I think it's likely that you don't normally see pretas, just like most people. Most people don't see asuras or nature devas either, but they're here.
So when I help someone non-physically experienced (by me) to move into "the light", I'm in fact interacting with a Spirit, and not the consciousness of the former physically living person?
In all likelihood, yes. If you're talking about helping someone "move on" after many years after they've died... the fact is they have already passed through the bardo and become someone else. Maybe even you're referring to helping pretas move on, but since you don't seem to understand what pretas look like, I very highly doubt this. Sometimes people really prefer to "blur the line" between spirits or ghosts and pretas. On the other hand, many lamas have it in writing that they are distinct concepts and oughtn't be confused or mixed up--even associated with one another. Pretas don't look like, act, or sound like the descriptions of "the spirits of the dead". On the other hand, many cultures throughout this world's history talk of two sorts of "ghosts," the ghosts of loved ones or haunting ghosts who were involved in something tragic, and then there's the atrocious awful ghosts of the dead, which are rather just generally unpleasant and miserable seeming. American paranormal subculture in no way helps this confusion.
You keep saying you don't see this yellow hue and these various lights of the bardo. Why would you expect to see someone else while they're in the bardo? Almost no humans in the entire world witness other people while they're in the bardo. Moreover, the yellow hue, or whatever color that is perceived, is based on what the bardo-being's consciousness is going through, not your own. Do I have recollections of passing through the bardo? Yes, of course. Do I witness other people passing through the bardo and say, "look, there's that yellow light." No, of course not. We're not even supposed to.