What are the connotations of "Arur Apam"?
Rashi: This teaches us that, even when Ya'akov was angry with his sons, he cursed, not them, but their anger. 1
Seforno: He cursed 2 their anger by lowering their prestige and lessening their livelihood, by dividing them 3 and scattering them among the tribes. Moreover, Levi would not take over the Kehunah until they earned it, following the sin of the Golden Calf. 4
Targum Yonasan: What he meant was that the town of Shechem was cursed when they attacked it to destroy it in their powerful anger, and their fury against Yosef was harsh.
Hadar Zekenim: Arur [here] is not a curse. It means that their anger should be diminished.
Prompting Bil'am's statement to Balak (23:8) "How can I curse those whom 'Keil' did not curse?" This is because Ya'akov's B'rachos were issued with Ru'ach ha'Kodesh
A Seifer Torah contains no punctuation. Perhaps we ought to attach the word "Arur" to the previous phrase to read "u'vi'Retzonam Ikru Shor Arur"
Yoma, 52b: This is indeed one of the five words in the Torah which is ambiguous in this way. 1
Torah Temimah (note7, citing the Maharsha): It is amnbiguous per se, but became clarified when Ezra fixed the Trop, which is Halachah le'Moshe mi'Sinai.
What did Ya'akov mean when he stated that he would 'divide them within Ya'akov and scatter them in Yisrael'?
Rashi #1: He meant that he would separate them from one another, in that Levi would not be counted as one of the twelve tribes.
Rashi #2: He decreed that Shimon would be poor, by virtue of their profession (Sofrim and Melamdim), 1 which also forced them to scatter far and wide to find Parnasah; whereas Levi would have to travel far and wide to collect T'rumos and Ma'asros in the granaries. 2
Seforno and Targum Yonasan: Refer to 49:7:1:2.
Rashbam: By scattering Levi throughout the land, he ensured that Shimon would be separated from him.
Rashi's two explanations seem to pertain to the two sections of the Pasuk, respectively (the first one to "Achalkeim be'Ya'akov", the second one to "va'Fitzeim be'Yisrael").
Rashi: His decree on Levi was more respectable, presumably because of their elevated status. This in turn, may well have been rooted in the fact that, already in Egypt, they were known as righteous scholars - See Rashi and Ramban on Sh'mos, 5:4.
What did Ya'akov hope to achieve by separating Shimon and Levi?
Targum Yonasan: As long as the two brothers remained together, no kingdom would be able to stand up to them. 1
רש"י: וזהו שאמר בלעם וכו': מה הראיה משם?
גור אריה (במדבר כג,ח): כתוב "לא קבֹּה" בלשון עבר (ולא 'לא יקוב')- משמע שהיו ראויים לקללה ואעפ"כ לא נתקללו.