Fair points, but let's take a more precise look at it. I think Nino is actually more likely to win than Ichika or Miku, and the winner will be Nino, Itsuki, or Yotsuba.
Trying to decide who's going to be the winner based on what Fuu thinks is pointless. The character is explicitly written to show as little emotional response as possible, because Negi wants us to be uncertain who will win. Instead, our best bet revolves around looking at story structure and character arcs. With ~30 or so chapters left, we can safely assume 2-3 major arcs remaining. That is enough room for one more "reversal of fortune."
A "Reversal of fortune" is basically the fundamental structure of all stories. Character starts well, things go bad, then things get good again. Lessons learned along the way. Luke starts happy, gets sad when Obi-Wan dies, gets happy again from blowing up the death star. Chitoge starts happy, gets cucked, and then gets happy again in Nisekoi. This is the basic formula for anything that's not a tragedy - in which case it's the opposite, start sad, see a glimpse of hope, then fall into despair.
With that in mind, look at 5tobun. 30 chapters left, there's only room for one more reversal for each character, at most. The bride's reversal - the final reversal - has to happen at the end of the manga. In this current arc, we are likely witnessing Ichika and Miku's final reversal - both are in a bad spot - morally, or emotionally - and this arc will see them return to happiness by the end. They don't have enough time to undergo another reversal without it feeling rushed. Miku can't recover, then fall immediately into despair again. You lose all semblance of pacing.
The winner will be the one who gets crushed closest to the ending. That means, right now, they have to be (relatively) happy. Which is basically Nino, Itsuki, and Yotsuba. They have to be happy to fall into despair, they have to fall into despair to win.