Is the first Umrah considered valid despite seeing brown blood after returning from Mecca, and is fasting on the days that followed valid, and what is the ruling on the two subsequent Umrahs performed on behalf of the father, and is the marriage contract valid?

Your 'Umrah is valid, and so is your marriage contract. What you saw after the 'Umrah is a brownish discharge (kudrah) that is not considered menstruation unless it is connected to blood. It does not affect the validity of the 'Umrah or the fast. Beware of obsessive whispers (waswas).