Hajj-e-badal

Q: I am looking for a good source for Haj-e-Badal. I have performed my Haj and have wish to perform Haj for my dad who is no more. I will be doing it with my money, so I believe I can do Haj-e-Tamattu also. Please correct me if I am wrong.

Fasting on Mondays

Q: Is there any truth to the claims that Nabi (sallallahu alaihi wasallam) fasted on Monday because he was born on a Monday. If it is true, is it permissible to use this to say that one can celebrate his birthday?

Entering into a partnership with a person whose capital will be from an interest bearing loan

Q: My brother wants to enter into a partnership business with another person whose initial investment in business is taken from an interest bearing loan. Is he allowed to enter into a partnership business with him? Will the profits earned by that business be halaal or haraam?