I've had the same hang-ups, to be honest, except I'm the Mono partner. It got to the point, where I basically sat down and told my partner that if I were to put a CD together for him (ah, the days of mix tapes...
), that I needed to know how he felt about a song like, for example, "Just the Two of Us" - because it's never really going to BE just the two of us.
He told me to relax and do what I wanted. That it didn't make him uncomfortable and he gets it. So okay... *I* still feel that oddness, but saying things like that doesn't make him uncomfortable, which was part of my worry.
As far as terminology, I tend to use, "I love you like no other," and he can use it back without it sounding like he loves me more, or better, or anything like that. We just sort of fell into using that phrase.