What is the ruling on polygyny in the mentioned case, and is the money spent by the wife considered a debt that must be repaid, and how can the problem of the wife's insistence on divorce or khulʿ due to polygyny be resolved, and what is the ruling on the wife reprimanding her husband because of it?

If you are capable of polygyny and ensuring justice, then there is no blame upon you. You should treat your wife well and try to persuade her. If what your wife spent was a donation, then it is not obligatory to repay it. However, if it was a loan, then it is obligatory to repay it. If Allah has blessed you with abundance, then it is part of perfect kindness to repay some of what she spent on you, even if it was a donation. We advise you not to rush into polygyny. If your wife suffices you, then it is better not to practice polygyny to avoid her disobedience or the disintegration of the family. However, if you need to marry a second wife because she is not chaste or for a similar reason, then try to convince her and seek mediation from someone of respected standing. Make it clear to her that it is not permissible for her to seek divorce (ṭalāq) or annulment (khulʿ) unless she is unable to uphold the limits of Allah due to her jealousy. Rebuking a husband with insults and curses is a major sin.