#1 The barrier effect - There is likely no single bit of information or insight that someone else can (or should) provide that will allow you to move beyond this point...this is an insight that is uniquely significant to you and for you alone to realize ...otherwise it will not have the proper importance or value to you. We can give some hints, some indicator of the direction to take, but beyond that we know to stay silent.
#2 Monroe's map of the Astral...I think your outlook on this is correct...take it as a "provisional belief", one that is good for current exploration but also open to re-definition as our knowledge increases...
Physical Reality....leads to Personal Astral Reality (Personal Dream Zone)...leads to/blends with the Collective Astral Reality/Afterlife Zone...which leads to the lower and upper Mental Planes...and so on, if you follow the Theosophical line of thought...(I don't pretend to know except that my own experience seems to have led at least into the lower Mental Planes)
The personal Astral is your own individual dreaming area: you have your personal learning experiences here, but you are segregated in that your uncontrollable emotions are kept away from the "collective areas" until you learn proper control.
This is just ONE of many ways to label our experiences here...choose your own labeling system as you move along. This is the way I see it at the present time, a provisional belief, and as my information changes, my categorization may change as well...
As for where you may find your "guides"...I guess that depends on a few things...I have looked for and called for mine, but I have had no response. It has been suggested to me by someone who I admit knows MUCH more than I know, that guidance may not be necessary at my level, that "they" prefer to observe how well I perform on my own, as it were. I did have one experience where I was obviously attended by another entity into and through an exciting experience (Fieldtrip) and another time when someone accompanied me during a visit to my recently deceased father. Other than that, I have been on my own or they have remained in the background.
As such, I'm not sure there is a "guide zone" to speak of. Some people can simply call out for them...that hasn't worked for me. The concept of "Intent" is very important nonetheless, and this can make all the difference at the right time.

Personally, I am thinking that guidance can come at any time, wherever you are... but they leave you on your own until you absolutely need them. In a sense, it is a perfect teaching system, brutal but fair and astonishingly effective.
As Szaxx told me once and "they" told me once...you are never given a task that is beyond your abilities. It may push you right to your personal breaking point, but it won't be any more beyond what you are capable of.
#3 You are at a point I was a few years ago...I wondered if any guides were listening, did they care?
They DO care, they are watching for how you respond, the quality of your response. "They" may consist of otherworldly guides; they may also be one or more aspects of your Higher Self(s)...
Just know that this is an especially lonely time that many of us are going through, those of us searching for a higher, deeper truth. Keep the faith.
You are being watched and assisted and strengthened...that much even I have become aware of...
#4 Yes Kurt Leland -If I could recommend one book, it is The MultiDimensional Human.