Yes if you get hit with one it will hurt
Because the air pump in a bb gun makes the bb feel like a pinch
Yes
Hurt, Yes. Kill most likely not.
Yes it could cause problems.
YES!
YES! Very much.
No
No, as long you don't use metal BB's, any plastic, 6mm airsoft BB's are good to use.
No.
70 FPS is considered low for a bb gun, of course if you were shot with it it would still hurt.
They can, if someone conks you with a BB gun. A shot BB can hurt like crazy, depending on its speed and the location it hits you. If the BB hits your eye, then you stand a very good chance of being blinded. In the Army, I was hit on the knuckle of my thumb with a BB fired from a low-pressure Daisy Red Ryder . . . it carved a nice half-sphere right out of the knuckle bone. Imagine what a CO2 or multi-pump BB gun could do!