Maoyuu Maou Yuusha/WMG

Several of the technologies and ideas the Demon Queen has originate from our world

 * I'm not sure what you mean by this WMG. For starters, do you mean that these measures have been implemented here or do you mean something like... she used her magic and research to find out about ideas and such from a world like ours?
 * The latter.

Young Merchant and Grand Princess Fire Dragon
End up becoming a couple, because Pair the Spares.
 * The Comp Ace manga seems to confirm this. She sent him to "battle" her father; apparently, victory was a condition for winning her. He negotiated rather than fighting, and Archduke Fire Dragon cheerfully declared himself defeated.