A Matter of Life and Death

How was the mercy seat in the earthly temple a type of Christ? Why were they rejoicing? Why was the anger of the LORD kindled? How did God lay the foundation of salvation for Adam and Eve? Why was David displeased at the LORD? Is sincerity an indication that the True Gospel is being preached? Who were these chosen men of Israel that David gathered together? Why is it vital to worship only Christ as He is set forth in the Word exactly?