So, can anyone clear this up for me, please?
Yes.
I can. I doubt I can do so with a simple post here however.
Doing so will be an important part of my next book on Satanism.
For now, let me suggest that in addition to the answers you have already been given here which I feel are essentially correct, you are also leaping to some conclusions that I would suggest are unwarranted.
First,
if you yourself come to discover that magic is real then please remember that Anton LaVey made a careful point of explaining that the unknown magic of today will likely become the known science of tomorrow.
Second, anthropomorphization is a common part of how the mind works on deep levels but does not have to be a
description of what is real as much as a
formula for making certain things work.
For example, you seem to equate "forces" with "entities" such as demons. Well, electricity is a force but very few today would assume it is a demon. If I wish to use electricity I can use a switch to turn on the lights. My flipping the switch is a formula for using electricity to turn on the lights.
If I use the anthropomorphization of a force and this results in magic working that does not mean that my mental "switch" proves there are devils doing the dirty work. My use of the names of old Gods and Devils in ritual does not require that they exist but does affect my mind and emotions in specific ways. It means that using this mental tendency can potentially produce an effect. And that is what the real magician seeks - results.
I see the same kind of confusion offered when someone has a heart attack, experiences a near death experience, later reports being out of body, observing events at a distance, later verifying that the events proved to be correct and then declares, "Therefore I know there is a God!"

"God" has nothing to do with it. Maybe he has acquired some evidence that an out of body experience is real (and many would even debate that on the basis of his experience). However, leaping to the conclusion that he will survive death and live forever in heaven with God is
not justified on the basis of that experience.
There are other suitable explanations that do not require an afterlife, much less "God".
I would encourage you to read the relevant portions of
The Satanic Bible again and grasp the overall premises upon which Anton LaVey suggested the practice of ritual magic. You might consider also reading the relevant portions of
The Satanic Witch regarding ritual.
The dark force we call Satan has multiple meanings all of which are spelled out in
The Satanic Bible and in ritual where you are expected to practice a willing suspension of disbelief, you are then free to take any and all of the old Gods and Devils and use them in the manner that moves you on unconscious levels to hopefully evidence the supernormal.
...If you want to try to do so.
But if this is
not your cup or tea you do not have to do so at all.
Satanism is always about "Indulgence, not compulsion".
Greater Magic is strictly an option and
not a requirement for the Satanist.
If you apply Lesser Magic effectively you may never find any need for Greater Magic at all. Ever.
Quite seriously, ask yourself what you want in life. Wealth? Health? Power?
There already exist numerous ways to achieve all of these and Lesser Magic exquisitely and directly targets all of them.
Lesser Magic is often already known for why it works and does not have the potential problem of requiring that you change or enlarge your view of reality to make it "work". You can easily grasp that Lesser Magic already works just as anyone can understand how stage magic works once you are shown the tricks.
Greater Magic is dealing with issues that are less popularly understood and operate in the darkness of unconscious mechanisms rather than in the conscious light of already understood mechanisms of human psychology where Lesser Magic exists.
So Lesser Magic is, in my opinion, far more accessible and practical for most Satanists to employ. Greater Magic requires being able to perform some very clever self-manipulations with issues of perception, evidence-testing and authority-rejection.
Greater Magic is simply harder to do. I do not state that as a challenge but simply as a statement of fact.
You really have to have the kind of personality that is attracted more to the exceptions of the rule, than the popularity of a rule. The sorcerer tends to be enthralled with the unusual, the white crow that proves that all crows are not black.
Just as it has been suggested by Anton LaVey that a person is born as a Satanist, I feel that so too are some born to be drawn to Greater Magic.
So if you find the entire concept of Greater Magic does not work for you, good! Don't waste your time trying to fit your round peg into the Greater Magic square hole. Be yourself.
If you are attracted to it you will not find yourself trying to make it fit into your view of reality.
You simply won't be able to leave it alone.
