I know it is expensive, but any thoughts on the romantic seine dinner river cruise?
Perhaps you didn't see this other current thread: https://community.ricksteves.com/travel-forum/france/seine-cruise-or-dinner-cruise
We enjoyed Le Calife, which gets good reviews. The food was good and I felt it was good value. Can't rate the romance factor, though, as we were a group of four women.
If you aren't married to the idea of a boat cruise, try Bustronome. The views are amazing and the food is quite good.