If this clearly refers to Solomon, then does that mean it has no other meaning?
So the line of David -- and the line of the future messiah -- must pass through Solomon.
Huh? God fulfilled his promise to David, in the person of Solomon. That this takes on a second, Messianic meaning does not mean that the fulfillment of it must follow the same path, does it?
SD
All subsequent kings of Israel were of the line of David through Solomon.