Is it permissible for a married woman, who is suffering from psychological and physical pressures due to living with her husband's family and supporting them, and the lack of privacy and comfort in her home, in addition to her inability to practice her religious devotions freely, to ask her husband to move to an independent home, or to leave the marital home and return to her family's home?

You are not obligated to serve your husband's mother or his relatives, but volunteering to do so is a noble deed. You have the right, from your husband, to be provided with a suitable, independent dwelling, and you are not required to live with his family, as cohabitation with them might cause you harm and damage.

If your residing in the dwelling exposes you to unlawful seclusion (khalwa (definition)) and impermissible mixing with his brother, then you must avoid that and maintain your lawful hijab (definition).

Your effort in household chores and your excellent devotion to your husband, with a sincere intention for Allah, will be greatly rewarded.

If your husband spends on his brother as a donation, he has no right to demand repayment for what he spent. However, if he spends on him with the intention of being reimbursed, then he has the right to reclaim what he spent. Partnership losses are proportional to the capital invested.