Above (verse 27), Eliezer blessed for the Chesed and Emes that Hashem did for Avraham. Why did he omit Chesed here?
Malbim: It was Emes to get the girl destined for Yitzchak based on Mazal. Avraham knew via astrology that she was in Charan. Chesed is above nature. He did not know that she is from his family. According to Eliezer's claim that Avraham demanded this, there was only Emes.
Why did Eliezer tell them that he blessed Hashem?
Ha'Emek Davar: This showed them how sure he was that they will consent. If he had any Safek, he would not bless!