J.J.
Hi K., I'm no expert but I went through something similar with my ex-husband. Most of his issues with me stemmed from his the abuses he suffered from his family when he was young.
It sounds like your fiancee is having trouble adjusting to people being in "his space". How long was he alone before you moved in? All too often when someone complains about the small stuff (such as things being out of place), it is because they feel threatened and enroached upon. If you really want to try to keep this relationship, I would recommend family counseling. If cost is an issue, there are places that will bill insurance or even work on a sliding fee scale.
Good luck! J.