Questions on Vayeishev

How could Yehuda and Reuvain allow their father to think that Yosef had died?
What was Reuvain's assumption of Yosef after he didn't find him? Did the other shvotim tell him that he was sold?
Why does it say in posuk chof hey that after they threw Yosef into the pit, they sat down to eat. What's the point?
Why, from all of the shvotim, was Reuvain the only one who wanted to save Yosef? Was there a consensus among the rest of the shvotim to kill Yosef? How can that be?
Why did Yosef need the second dream? Didn't the first dream already make the point that Yosef will be a ruler over them?
Why does the Torah mention the hatred about the initial dream a second time in posuk ches? We already know their feelings from its mention in posuk hey.
Why does it say in posuk hey that the brothers hated Yosef even more because of a dream? It should have first mentioned the dream before their feelings about it.

Response:

We will attempt a general approach that will give a better understading of this subject without actually addressing each question.
A basic pretense that the brothers were not overcome by simple sibling rivalry is crucial to understanding the parshah. Similar to the race for children of the 'Imahos', our ancestors were well aware of the eternal national effect of all their actions. Their decisions were made based on what they were able to comprehend as being the most beneficial for the future of klall yisrael. As is well known, even Hakodosh Baruch Hu interacts with the world based on the human perception of bes din. With this in mind, we can assume a very well-meaning, Torah inspired, humanly flawed  approach to all that transpired in these parshios. Chazal critique on Yakov Avinu's open display of special treatment of Yosef and comment that this helped lead to the slavery in Mitzrayim. It is this backing that allows us to say that, although Yakov avinu definitely had great intentions, there was some level of error made in his decision.

The brothers' assumption that Yosef was attempting to overthrow the family and rebuild klall yisrael just from his own children was well founded, but yet mistaken. However, all their actions were done for what they deemed - as the great Sanhedrin of their time - as assuring the future of the bnei yisroel as exactly that - Bnei Yisroel. Their father, being the last of the avos, and the children being his mitasoh shlaimah; klall yisroel.

As per each detail of the story, a good look at the classic commentators in the mikraos g'dolos should answer most of the questions.
Gut Shabbos!........D.M.