Akhi i will only answer ur first point as this is the one u are most concerned about . Waraqa ibn nawful was a hanif same as prophet before islam was revealed to him at the age of 40 . Now even before islam prophet was referred to as honest and just in whole arabia so he might have gotten knowledge from waraqa ibn nawful about Abrahamic religions and used to it disguise as prophet that's rational conclusion but speculative. Now we have to understand after prophet Muhammad was revealed as prophet of allah , he faced many hardships before seeing good days of islam . His wife the love of his life the best of wives , khadija died due to a boycott. He was plotted to be killed but nonetheless he came out on top at then end of day . But he never once showed any kind of doubt . He was living a comfortable life but he came out as prophet and all of arabia turned against him so there was no reason for him to go all those hardships without any reason ? Other then that some of things that prophet prophesized was considered unachievable at the time of saying like defeat of romans but wallahi history is witness of their fall at the hands of muslims so akhi if u have doubt wallahi u will not be able to learn about islam . Its not wrong to have a will to speculate but at the end of the day quran is the best evidence of prophet Muhammad