Is it permissible for the wife to save from her well-off husband's money an amount equivalent to her dowry stipulated in the marriage contract and to dispose of it through charity and sacrifice (udhiyah), and is it possible to adjust the amount of the dowry due to the change in currency value?

If your husband does not deny your deferred Mahr or delay its payment, it is not permissible for you to take it from his money without his knowledge. However, if he denies it or delays the payment of the due deferred Mahr, and he is not in financial difficulty, then it is permissible for you to take it from his money without his knowledge (the principle of "taking one's right"). It is not permissible to take more than the due right, even if the currency's value depreciates, unless the currency in which the right was established is abolished.