approximately 5.5 ltrs.
Tidal volume is the volume of gas inhaled or exhaled during a normal breath. The tidal volume of an average adult is approximately 500 to 600 mL.
In a human, blood makes up about 7% of the body's mass. Thus to get an idea you would need to weigh your 9 year old and work it out. A typical adult of about 70Kg has a blood volume of approximately between 4.7 and 5 liters
About One Hundred quarts in the Human Body
No. If you're male you're borderline skinny and if you're female you're right in the ballpark for a healthy weight.
70kg on the charts
No, it is not. "For every action there is an equal and opposite reaction". The 70kg person is pulling just as hard on the Earth as the Earth is on the 70kg person, i.e. about 686 N.