About 2.2 pounds.

Energy in food.  Multiply Calories by 4 to get kilojoules.

Nap.

In Australia, tag is called chasey.  Kiss-chasey is just a more fun version of that.

Absolutely worn out, drained of energy like a horse that has just been gelded (sorry).

Time to cease one's labours.

Cutlery in Australia, silverware or flatware in America.  Australians consider it a hardship to hack at food with a fork instead of holding it with a fork and cutting it with a knife.

Stunned.  In cricket, if a batter can hit (knock) the ball to the boundary without touching the ground, they score six runs.  The speaker is feeling like a cricket ball which has been hit very hard.