Does reading the rejected suitor's messages and the inclination one feels toward him after performing Istikhara have a meaning, and is sending a message to clarify the situation permissible, and what is the interpretation of seeing one's father in a dream after performing Istikhara prayer?

We do not interpret dreams, nor is a dream a condition for the validity of Istikhara, nor is any practical religious or worldly ruling based on a dream. If the suitor is pleasing in his religion and character, do not reject him and do not pay attention to the dream. It is permissible to read the suitor's messages and reply to them as needed and within the Shariah guidelines.