Is the questioner's objection to some of God's legislations, such as polygyny and the rights of men and women, considered disbelief (kufr)?

Man is not held accountable for mere thoughts unless they lead to words or actions, and he must resist them. Disliking these thoughts is a sign of faith. One must submit to the rulings of Islamic law. Guardianship (qawamah) is for organizing family affairs, not for domination, and a wife's obedience to her husband has limits. Among the wisdoms of the waiting period (iddah (definition)) is to ensure the purity of the womb.