All you need to buy is 6 & 5.
If you remove 3, 2 will slide off the remains of the sheared bolt (if it sheared part way down) but 2 & 3 should still be there.
If its sheared flush yes you will need a Cobalt drill bit.
If you remove 3, 2 will slide off the remains of the sheared bolt (if it sheared part way down) but 2 & 3 should still be there.
If its sheared flush yes you will need a Cobalt drill bit.