Is it permissible to marry a second wife despite fearing a change in circumstances and future poverty, and is this marriage a right for the purpose of chastity and lowering the gaze, given the aforementioned reasons of the first wife's inability to satisfy the husband's desires, and the unwillingness to divorce her?

Your fear of poverty or changing circumstances should not prevent you from getting married. As long as you intend to marry to protect yourself and guard against the forbidden, while being keen on keeping your first wife, raising your children, and pleasing your parents, then your marriage to another is desirable and blessed. Allah Almighty said: "If they should be poor, Allah will enrich them from His bounty." This is a promise of wealth for those who marry seeking Allah's pleasure. Furthermore, lowering the gaze from what is forbidden is among the most beneficial ways to protect one's chastity and purify the heart.