[Advaita-l] Pitru Rina and progeny

[Aditya Kumar]

Namaste All,
Please delete this post if you feel it is irrelevant to this group. 
I understand that to be free from Pitru rina, one should procreate and bring forth progeny. For those that do not follow this rule, the doors of the upper worlds are closed, as per Shastras. The only exception to this rule is to those who take up sanyasa right after brahmacharya. Because sanyasins are considered as dead. But there seems to be a lot of exceptions. I request advice from learned members :
1) What if parents cannot conceive? Is surrogacy allowed in Vedas?2) What if parents have only female child?3) What if a man decides to spend his lifetime observing strict rules of brahmacharya (Like Bhishma)? Although, I don't think people generally would have a compelling reason like Bhishma to choose the Brahmacharya mode of life. 4) What if a person finds a lot of fault in Grihasta mode OR if a man cannot fend for himself save his dependants OR testing times like war torn nation or great misfortune?
Thanks