What are the connotations of "va'Teishvu be'Kadeish"?
Rashi (in Iyov, 22:8): It means either 'You were held-back' 1 or 'You spent a long time' - in Kadeish.
Targum Onkelos and Targum Yonasan: It means simply 'You stayed in Kadeish?.
See Torah Temoimah, citing Megilah, 21a, and note 37.
What are the implications of the term "Yamim Rabim" both here and in 2.1?
Oznayim la'Torah (in 2:1): It implies a. literally a long time and b. bad times. 1
And by the same token, good times seem to be short - as in Vayeitzei Bereishis, 29:20.
What is the meaning of "ka'Yamim asher Yeshavtem"?
Rashi: It means that they remained in Kadesh as long as all the other travels put together. They spent thirty-eight years in total in the Midbar after the Meraglim, 1 nineteen years they spent in Kadesh and nineteen years traveling, 2 at which point they returned to Kadesh. 3
Rashbam: It means ?as you full-well know?. 4
See Sifsei Chachamim.
See Oznayim la'Torah, who, citing the Seider Olam, actually inverts the order and elaborates.
To teach us the Chesed of Hashem, who gave them respite for such a long period even after the harsh decree. See Oznayim la'Torah.
See Oznayim la'Torah who cites the Ibn Ezra's explanation and queries both explanations.