a fiance to be alone with his fiancee

Praise be to Allah.

With regard to your question, it is not permissible at all for you to be alone with this man, because the Prophet (peace and blessings of Allaah be upon him) said:

“No man and woman are alone together, but the Shaytaan is the third one present.” 

There is nothing wrong with talking to him from behind a screen, such as on the telephone, so long as this is done in a proper manner, with no suspicious talk and no fitnah (temptation), and as long as you do not overdo it (or talk too much). You should only talk as much as is necessary. 

With regard to his claims about the importance of knowing one another before marriage, this is not right. It is sufficient to ask some trustworthy people and to find out about the prospective partner so as to be certain and have peace of mind. We ask Allaah to make things easy for you and for him. May Allaah bless our Prophet Muhammad..