In the last moments here before Shabbat, let me just point out a few more things to consider:
In the last posting we see that Yaakov takes his grandsons into his hands and then blesses Yosef. What exactly does that mean? It is possible that Yaakov saw his grandsons as extensions of Yosef and by blessing them he also blesses Yosef. Note that he gives his grandsons their blessing just a few verses later.
We see also that Efraim is placed before M'nashe, not in the order of their birth. This continues a long tradition found in B'reishit most notably with Yaakov himself being the last recipient, albeit through deception, of a blessing meant for the first born. Yaakov gives the blessing knowingly, though. He clearly gives a double portion to Yosef by giving his two sons a blessing and a portion in future inheritance.
But by giving the blessing to the older of his two grandsons, Yaakov is placing the younger before the older twice: That is, he has now place Efraim before M'nashe but by giving them each a blessing he is also placing Yosef before R'uven.
This is particularly interesting because in previous generations, the younger who got the blessing was the second oldest (Yitzchak over Yishmael, Yaakov over Esav) while here there are many brothers who were born after R'uven before Yosef was born, yet he gets the blessing.
What was so special about Yosef in Yaakov's eyes? Obviously, the first point is that Yosef is Rachel's oldest son and Yaakov only really loved Rachel from his four wives.
Beyond that, though, Yaakov identified with Yosef. The midrash at the beginning of parshat Vayeshev lays this out to begin with by noting that what happened to Yaakov also happened to Yosef. Yaakov's brother hated him, Yosef's brothers hated him. Yaakov's brother wanted to kill him, Yosef brothers wanted to kill him. Yaakov had to go into exile, Yosef had to go into exile. And so on...there are many other similarities.
So now when it comes time to give these blessings, it is clear that Yaakov will favor Yosef because he sees Yosef as an extension of himself.
Yaakov goes on to tell the brothers what will happen to them in the future and blesses them, as well. The parsha goes on to relate what happened when Yaakov passes away and after and leaves off with the death of Yosef and his burial in Egypt.
We never really find a reason why the brothers didn't go back to Canaan after the famine. However, it is clear that the fact that they don't plays nicely into the prediction of the diaspora given to Avram, as we noted previously.