About 2.2 pounds.

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

Nap.

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

Time to cease one's labours.

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.