a) true, the pressure is 1atm. On how big area? What force does that mean?
b) the scenario that is, in my opinion, dangerous, is a rupture of the capsule that is pressurized to 1atm surrounded by near vacuum. Followed by a collapse of the tube that results from the pieces of the capsule flying in all directions.
However the biggest problem I see from my chair is keeping a relatively fragile tube stretching hundreds of kilometers airtight, undamaged and secure from pissed farmers, drunk idiots, gun fans, vandals and other similar factors.