How do I deal with my family who sometimes mistreat me by reproaching me for not getting married and for remaining with them, despite my contributions to household expenses and my eagerness to honor them, while also wishing to preserve my dignity?

Parents have a great right to righteousness and good companionship, even if they treat one poorly, and this right is guaranteed by the Sharia. One must be patient with their ill-treatment and continue to be righteous and kind to them. Practical advice includes: patience and seeking reward from Allah, continuing to be righteous and kind to them with gifts and kind words, advising them with wisdom and good counsel, diversifying methods of da'wah (invitation to Islam), seeking help from scholars, striving to earn lawful sustenance for marriage, and persistently supplicating for their guidance.