Brother Abu Musaab is right,
Aside from the plain obvious that this brother seems to be paranoid and deceitful and no good for any girl, and that he may be Sunni yet carrying around beliefs and behaviours that scar his faith and status as a muslim, aside from all that you being a Shia is not just a small issue that shouldn't be dealt with, and Mutaa marriage is nothing compared to other great failures Shia Imamiya carry in their doctrine that practically nullifies faith.
If you are a reasonable person you need to open your mind to the fact that God's religion cannot have mistakes, and therefore when you yourself feel with your natural instinct that something such as Mutaa marriage is wrong and sinful yet the Shia clerics are encouraging it and pushing it and constantly come up with different stories as to why it should remain, that should tell you at the very least there is something not right.
However, in relation to your own question, I still think that as a person this man is not a trustworthy person to start with and you should seek a marriage partner elsewhere, and if you're seeking God truthfully, you should insha Allah find him. There is a supplication I believe: "God show me the truth as truth and provide me with the ability to follow it, and show me falsehood as falsehood and provide me its avoidance" You can also say "God grant me your true guidance and leave me not to people's misguidance."
Wassalamu Alaikom