When I read that you were at the halfway point in mixing this tune, I knew it would be damned good. Not much to do to improve things with the next half. It is a very polished, professional sounding mix as it is. I would agree with the opening vocal being a bit subdued, but that's an easy fix. I love your use of reverb and delay on the guitar fills and solos, it adds a lot to the feel.
If I was to make any suggestions at all, and please take this with a pound of salt, some of the guitar fills sound a little stiff to me, like it is trying too hard to stay on the grid. Obviously, every guitar player thinks they could do better, but I'd love to hear it crying a little more to fit the ballad. Hope that makes sense, it's a very small thing.
Either way, this will be epic when you are done.