At different times during the history of Israel, the boundaries have been slightly different. I think it depended on the ability of the people to manage the Land along with their spiritual standing with the L-rd. What good is is it to give land and allow the wild beasts to multiply faster than the people can handle it, etc. Also, the Land belongs to the Jewish people, but the L-rd only allows them to live in it if they are submitting to Him. He allows a grace period then if all else fails, He allows their enemies to harrass them and eventually take their land for a limited time. He made an eternal covenant with them.
However at all times, the area of Judea and Samaria has been part of Israel proper. (This is the area the journalists term the "West Bank" & this is the area which Arafat wants)
Generally speaking, the Mediterranean Sea is always listed as its western boundary and in places, the Jordan River is listed as its eastern boundary except for the Golan Heights, which is included in Israel's territory. The southern boundary is the small wadi called the brook of Egypt which is just southwest of the Gaza strip. The northern boundary is the spring which forms the Orentes River (in modern-day Lebanon)
The boundaries for the future Messianic Kingdom are larger than what Israel has now - Israel will stretch to the Euphrates River in the north. Of course in that day, many will want to be part of the nation of Israel because the King of all kings will be reigning here!
I will get back to you with some Scripture on this in a day or two & also answer your other questions. Shalom!