What is the ruling on my asking a suitor about his salary and his father's profession, and is the result of Istikhara that he rejects me?

The preponderant opinion is that a person should proceed with a matter after performing Istikhara, and not abandon it unless Allah diverts them from it. Therefore, the suitor's withdrawal from the engagement might be the good that Allah intended. As for the suitor asking about her salary and her father's work, there is no harm in that, and emphasis must be placed on his religious commitment and character. You made a mistake by speaking with him on the phone and meeting him without a mahram, for what is permissible for the suitor is looking, not privacy; because she is still a stranger to him.