Sounds good. Also add Naruto has been fighting for a long while, and has sustained multiple injuries.Kushina was full uzumaki..
Kushina had a higher compatibility
Kushina's chakra was unique which i believe also helped
Seal was weakened so its possible there wasnt as much strain from it being ripped from the body when the seal is at its strongest (this one is only a guess )
Hes been quite some time without sleeping.