Is it permissible for the fiancé, who is unable to solemnize the marriage contract due to current circumstances, to speak with his fiancée and express his feelings to her for fear of temptation?

Your fiancée is a stranger to you, and it is not permissible to speak with her except out of necessity and to the extent of that necessity, using permissible words that do not incite temptation. Therefore, informing her of your feelings towards her is not permissible in Islamic law. You should appoint a man from her city to conduct the marriage contract. After it is completed with all its conditions and pillars, she becomes your wife, and everything that is permissible for a husband with his wife becomes permissible for you.