There were no failing words among all of the promises of God. That was good news for the people of God in Joshua’s day, and this is good news for the people of God today, whose very lives, just like theirs, depend no less upon God’s promises.
The point of this passage is that God is so great and so worthy of worship and trust and obedience that a single act of disobedience against him—a single bite of of a fruit—deserves to have the whole creation come crashing down in response.
Eve was not exactly like Adam. God made a woman, not another man. But she was clearly the same kind of creation as he was. Someone with whom he could be fruitful and multiply; someone who was a suitable helper for him. And he rejoiced.