1) What is our relationship with God as per vishistadvaita?
2) Why should God help and protect us? What motivates him to do so?
According to Vishishtadvaita, there are nine types of relation a jiva enjoys with Lord Vishnu which I am quoting from here :
Pitra-Putra Sambandha: the relation between a father and a child.
Rakshaka-Rakshya sambandha: the relation between savior and the saved.
Shesha-Sheshi sambandha: the relation between owner and the thing owned.
Bhartru-Bharya sambandha: the relation between husband and wife.
Jñatru-Jñeya sambandha: the relation between knower and object of knowledge. Vishnu is the object to be known by the Jiva and Jiva is the knower since it has the ability to know itself, the Lord and the relation between the two.
Sva-Swami sambandha: The relation between property and its owner. Jiva is the property owned by Shriman Narayana.
Sharira-Shariri sambandha: the relation between the Self and the body. In Vishitadvaita, chit (entities with consciousness) and achit are said to form the body of Narayana.
Adhara-Adheya sambandha: relation between supporter and the supported.
Bhoktru-Bhogya sambandha: relation between enjoyer and the enjoyed.
It is believed in Shri Vaishnavism that the Lord showers His mercy upon seeing the sufferings of His devotees. He cannot bear the sight of His devotees suffering.