1)
How far westwards did the borders of the Reuveni and the Gadi extend further north in the area of the Plains (the Aravah)?
1.
Rashi: It extended as far as and including the River Yarden and as far as and including, the Sea of Kineres - on its western border.
2)
What is the meaning of "Ashdos ha'Pisgah?
1.
Rashi and Targum Onkelos and Targum Yonasan: It means below the pouring of the water from the high places 1 (the waterfall from the mountain-top - Artscroll).
1
Refer to Bamidbar, 21:15:1:1.