Why did God swear that the whole world would be full of His glory in Numbers 14?
Is He, in the end, only a vain god?
Or is something else happening here?

Hebrews 6:13-20 offers God's oaths as our anchor, sure and steadfast, during the storms of our lives.

Jeremiah 31:31 God will write His law on our hearts.
Revelation 22:3 We will look into His face, for He will have made us as holy as He is; full of truth and grace.

all the Old Testament covenants are found in Romans 8; God wants us to know that we are totally safe in Jesus. He wants no doubt, no fear, in our hearts on this account.

God will write His law of love on our hearts.
we will see His face, for we will be holy as He is holy.

God blessed David after David offered to build Him a house.
God gave David a fantastic gift; a universal throne, an eternal dynasty, an eternal name.
He has seen your worship, and is blessing you too.

Exodus 19:5 and I Peter 2:9 are God's promises to transform us into people that look like Him if we will obey His covenant. We obey Him. His commands rule us; and we become His priests.

God wrestled with Jacob, and called it prayer. Why?
Why must we fight God to get Him to do stuff?