The swords pretty long, and it even looked longer in the manga than it did when he sealed orochimaru (judging by the distance they was) Maybe it extends, since its no physical shape.tht doesnt mean he was close 2 naruto. he was just close enough 2 use it. i read the manga and tht distance doesnt look luk reachable with totsuka sword.
but when i said close i meant Nagato has to be very close to pain.
So itachi can seal him while he's using Chibaku tensei, They either both might die Nagato might get sealed, and itachi might get crushed If Susano'o cannot take it.