Does the suitor's lack of feeling happy, the existence of some problems, and the absence of seeing a vision or feeling a negative or positive sensation after repeatedly performing the Istikhara prayer, mean that his marriage to his fiancée, whom he considers to be of good character and religious commitment, is not the best for him?

Scholars have differed regarding what the one who performs Istikharah should rely on after doing so. The preponderant opinion is that a person should proceed with the matter after Istikharah, and only abandon it if Allah diverts them from it. Therefore, as long as your fiancée is religious and of good character, proceed with the engagement without hesitation, and rely on Allah Almighty, asking Him for ease and success.