>>How about "loved one"? <<

That's near enough the literal translation of the mainland Chinese term for 'spouse' - loved person.
Unfortunately in Taiwan (at least ten years ago it was the case) the same word means 'lover' in the carnal sense.

The English word 'lover' seems equally slippery in meaning.

Personally, I use partner in day-to-day speech. A large number of people assume this means I am lesbian. (Just as a large number of people assume that because I use Ms I must be divorced!)

WHen I think I can get away with it (when Steve's not there!) I have been known to refer to him as my 'not so good quarter'.