Let me answer question#4--this is a cut & paste from Chapter 7 "The Trilemma--Lord. Liar, or Lunatic?" but it directly answers why Jesus could not have been a lunatic.
LUNATIC?
If it is conceivable for Jesus to be a liar, then could not He actually have thought Himself to be GOD, but been mistaken? After all, it is possible to be both sincere and wrong.
But we must remember that for someone to think that He is GOD, especially in a culture that is fiercely monotheistic, and then to tell others that their eternal destiny depends on believing in Him is no slight flight of fantasy but the thoughts of a lunatic in the fullest sense. Was Jesus Christ such a person?
C. S. Lewis has written: "The historical difficulty of giving for the life, saying and influence of Jesus any explanation that is not harder than the Christian explanation is very great. The discrepancy between the depth and sanity of His moral teaching and the rampant megalomania which must lie behind His theological teaching unless He is indeed GOD has never been satisfactorily explained. Hence the non-Christian hypotheses succeed one another with the restless fertility of bewilderment."
Napoleon (cited by Vernon C. Grounds, The Reason for Our Hope) said: "I know men; and I tell you that Jesus Christ is not a man. Superficial minds see a resemblance between Christ and the founders of empires, and the gods of other religions. That resemblance does not exist. There is between Christianity and whatever other religions the distance of infinity...Everything in Christ astonishes me. His spirit overawes me, and His will confounds me. Between Him and whoever else in the world, there is no possible term of comparison. He is truly a being by Himself. His ideas and sentiments, the truth which He announces, His manner of convincing, are not explained either by human organization or by the nature of things...The nearer I approach, the more carefully I examine, everything is above me - everything remains grand, of a grandeur which overpowers. His religion is a revelation from an intelligence which certainly is not that of man...One can absolutely find nowhere, but in Him alone, the imitation or the example of His life...I search in vain in history to find the similar to Jesus Christ, or anything which can approach the gospel. Neither history, nor humanity, nor the ages, nor nature, offer me anything with which I am able to compare it or to explain it. Here everything is extraordinary."
Even Channing, the Unitarian writer, speaking of the lunatic theory (cited by P. Schaff) said: "The charge of an extravagant, self-deluding enthusiasm is the last to be fastened on Jesus. Where can we find the traces of it in His history? Do we detect them in the calm authority of His precepts? In the mild, practical and beneficent spirit of His religion; in the unlabored simplicity of the language with which He unfolds His high powers and the sublime truths of religion; or in the good sense, the knowledge of human nature, which He always discovers in His estimate and treatment of the different classes of men with whom He acted? Do we discover this enthusiasm in the singular fact, that whilst He claimed power in the future world, and always turned men's minds to heaven, He never indulged His own imagination, or stimulated that of His disciples, by giving vivid pictures or any minute description of that unseen state? The truth is, that, remarkable as was the character of Jesus, it was distinguished by nothing more than by calmness and self-possession. This trait pervades His other excellences. How calm was His piety! Point me, if you can, to one vehement, passionate expression of His religious feelings. Does the LORD's Prayer breathe a feverish enthusiasm?...His benevolence, too, though singularly earnest and deep, was composed and serene. He never lost the possession of Himself in His sympathy with others; was never hurried into the impatient and rash enterprises of an enthusiastic philanthropy; but did good with the tranquility and constancy which mark the providence of GOD."
Philip Schaff, the historian, wrote: "Is such an intellect - clear as the sky, bracing as the mountain air, sharp and penetrating as a sword, thoroughly healthy and vigorous, always ready and always self-possessed - liable to a radical and most serious delusion concerning His own character and mission? Preposterous imagination!"
LORD!!
Who you decide Jesus Christ is must not be an idle intellectual exercise. You cannot put Him on the shelf as a great moral teacher. That is not a valid option. He is either a liar, a lunatic or the LORD. You must make a choice. "But," as the apostle John wrote, "these have been written that you may believe that Jesus is the Christ, the Son of GOD"; and more important, "that believing you may have life in His Name" (John 20:31).
The evidence is clearly in favor of Jesus as LORD. However, some people reject the clear evidence because of moral implications involved. There needs to be a moral honesty in the above consideration of Jesus as either a liar, lunatic or LORD and GOD.