This type of language is fairly absent from the source material, but there's still some vocabulary to work from. Ahmul 'husband' and kiim 'wife'  are straightforward starting points, if more formal than endearing.

The possessive suffix -i 'my' can prove handy here. Attach it to any noun that might be used as a form of endearment (kuni 'my light', smoliini 'my passion', etc.), and you can form a wide variety of terms. How dragons or ancient Nords expressed endearment isn't well known, so expressing this through possession may be the most basic way without making too many assumptions.