My own experience is that these "how much point can this line possibly score" numbers are only clutter. I don't look at them. Maybe I should only show the possible points when a new line is established, and show some kin of alert when a line will be broken (the amount of possible points lost?).

Also, while I like the preview feature, showing the current tile-to-be-placed in two places simultaneously feels wrong. Maybe I shouldn't show it at all in the corner. But then what to do when the pointer is over an ineligible position? (which is always the case when you just placed the last tile)