Strength of schedule is calculated from the opponents projected fantasy points allowed for the WR position. The best rating is +16 which gives the player the advantage against the defense and indicates an easy opponent, the worst rating is -16 which gives the defense the advantage and indicates a tough opponent.
Rice is still not 100% (when was the last time that he was?) but is expected to be ready for training camp. Even if 100% healthy, Rice is far past his prime and the Seahawks prefer to run the ball, so there's no need to waste a draft pick on Rice.