Abraham the father of the east

Our father Avraham had 7 (or8) other children outside of Yitzchak .In fact the Torah says that Avraham got married once again and fathered another 6 sons. Each of the sons started another
nation. The question is Avrohom was 137 years old then ,what was the purpose of getting married again.
At that age Yitzchak doesn't remarry. Neither does Yakov. Why Avrohom?
Avrohom by nature was different from his offspring. Avrohom felt that he could and therefore should endeavor to influence the world. He saw however, that men like E-liezer, as well meaning as they might be lacked the courage and conviction to influence others.
Therefore the motive for Avrohom's remarriage wasn't to be taken care of. For that he trusted that Yitchak or even Yishmoel would respect their father.It was in order to change the idolatrous practices of the peoples of the near east that Avrohom was worried about.
This seems to also be the secret as to why Avrohom sent his sons away to the East . He gave them gifts. What kind of gifts did he give them? Rashi says a Shem Tumah!?
Now if this means that he gave them the power of impurity,how could a man that had battled impurity all of his life give them this impure power to use and succeed with?
The answer is simple ;He gave them the power to overcome the evil ways of the peoples of the east. In this way Avrohom made the world a better place, one that in the future would embrace the true unity of G-D!