‘Pride is the cause of all sin’
Did this begin with, and caused by, satan’s fall because he wanted to be equal with God and now is prince of this world to which we live outside of perfect communion with God due to the fall? The fall of man being caused by pride as well.
Yes, satan and his demons started this going against God, and wanting to be god without God, wanting to be an evil god -- more accurately said. Theirs was a deliberate and clear decision. Man's fall was not so radical -- he was partly misled by satan ("did God actually say you will die? no, He is afraid you will be like Him") and partly did not have the experience to say "no" to satan, he was rather naive. So man's fall is not like satan's fall, it is neither permanent, nor necesarilly a sign that Adam actually wanted to go against God, to overthrow Him. However, it was serious enough to fall into separation from God. God allowed this suffering of man so that man feels it and realizes that it is better with God; otherwise man might not be able to overcome the seed of pride that satan planted through his temptation.
‘love of self is the worst sin’
Thus, in part, the importance of ‘die to self to live in Christ’?
Yes, we give up the old man (the one fallen into sin), and put on Christ (The New Adam), His own incorrupt nature, and we become like Him, as He intended us to be from the beginning.
...the essence of pride is that man is separated from God. Having lost direct communion with God, man fills it with himself, his own understandings, findings, desires, etc. Consciously or unconsciously man lives as if he is God, or as if there is no God, hence man becomes the ultimate authority. Orthodoxy means to heal this by re-establishing the direct communion with God through The Grace of The Holy Spirit, and hence, heal from pride and passions. I guess we could say that we all inherit this pride since man was never intended to be without God, and that void will inevitably be filled by man himself; we are sort of walking around with a terrible illness and don't even know about it. We must have hope that God can heal us, it's easy for Him, but the hardest thing is for us to acknowledge the illness and understand the depth of this illness (guess you could say blindness -- we are blind to God, to the spiritual).
Did you just describe in practical terms the fall of man, ancestral sin, and our need for repentance?
(For understanding each other what I would call the process of repentance includes; regeneration, justification, and sanctification is what I think Orthodoxy refers to as Theosis)
Yes, basically, I have talked about the fall of man, the sin of being separated from God that we all inherit and which is the reason why we get infected with all other sins (so, the pride that fills the void of being separated from God). The path of Orthodoxy, if we are to talk about Theosis, has three stages: Purification (by fighting with and eliminating the passions), Illumination (God's own Grace intervenes and starts to illumine man in a palpable manner), and finally, Theosis (actual union with God in The Holy Spirit).
Part of my question is due to the fact that I struggle enough with the pride in myself I do see. What about (if you do agree subtle aspects of pride is indeed hidden within us) the pride we cannot see? As you said we must have hope, and I believe I do, that God can heal us. I agree the hardest thing is acknowledgement. Is having these deeper recesses revealed solely a matter of faith, trust, hope, and prayer?
Yes, things can be very fine and hidden, in addition to the more coarse, obvious passions; but, we should not dwell on it too much, we shouldn't think it's too hard; God can help us and give us His own strength and wisdom. The main thing is that we rely on God, not ourselves, otherwise we either fall into despair, or, the other extreme, the pride that we can be virtuous without God. So, pride can work in this direction, too -- that you fill the void of being separated from God through your own power and virtue, but in the end, you are still separated from God, still pride. God does not intend it like that; He actually wants to come into our life to heal us, and to be with us/in us permanently Himself. This is the orthodox concept of Salvation -- that God is not angry with us, too far from it; He simply means to heal us and to re-establish the relationship with us, which was stolen by Satan.