Do Exodus 32:13 and Deuteronomy 4:40 promise the Jews the land forever?

No. In Exodus 32:13 Moses is trying to persuade God away from the decision He had made to destroy the Israelites for worshiping the golden calf, and he poses it as if God had promised Israel the land forever. Moses says, 'Remember your servants Abraham, Isaac, and Israel, to whom you swore by your own self, I will make your descendants as numerous as the stars in the sky, and I will give your descendants all this land I promised them, and it will be their inheritance forever.' But God never said exactly that; Moses is conflating, or at least exaggerating, what God actually said, because God spoke about the land and the Israelites several times between Genesis 12 and Genesis 22. There is a real difference between God saying 'to you and your seed' and saying 'to your seed.' In Genesis 15 God says 'to your seed I will give this land,' naming the land of Canaan, the Hittites, the Jebusites and the rest, and the Israelites did take it over about forty years later, so God fulfilled that promise. But in Genesis 17:1-8 God says 'to you, Abraham, and your seed I will give this land forever,' using the same Hebrew word olam, and that is a different, spiritual context, the same one begun in Genesis 12 when God said that in Abraham all the nations of the earth would be blessed, not just the Jews, who did not even exist yet. Scripture makes a point of the fact that Abraham never received the land promise; Hebrews 11:8-16 says he never received it, because God is going to fulfill it in a far greater way, with a heavenly land that God Himself makes, an eternal inheritance. Our Christian Zionist friends do not want you going to Hebrews 11 because it is in the New Testament, and they want to keep the Old Testament separate so the New cannot interpret the Old, because that would answer the question and undo their Christian Zionism. And the land was plainly not given forever: the ten northern tribes were sent into oblivion in 722 BC, the two remaining tribes went into Babylonian captivity in 586 BC, and even after Ezra and Nehemiah they had only a portion of the land, which was obliterated when the Romans came. So when God says to Abraham 'to you and your seed,' it always refers to a future land in the kingdom of heaven, the new heaven and the new earth; 'to your seed' refers to the land of Canaan on earth, which they did receive.