All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, all perfect praise be to Allaah, Who guided you to Islam and we ask Him to make you firm and steadfast on His Religion until the day you meet Him.
We advise you to be patient and hold fast to the Book of Allaah and the Sunnah of the Prophet and be steadfast on them, and ignore the accusations of your relatives that you have gone astray. Indeed, the polytheists accused the Prophet and the Prophets, may Allaah exalt their mention, before him, of this and of more serious things, and Allaah Says (what means): {So be patient, [O Muhammad ], as were those of determination - among the messengers.}[Quran 46:35]. Therefore, you should be patient and steadfast and continue to call your family to Islam with wisdom and good admonition as Allaah may guide them thanks to you, and remember the Saying of Allaah (which means): {And who is better in speech than one who invites to Allaah and does righteousness and says, ''Indeed, I am of the Muslims''.}[Quran 41:33].
As regards what you mentioned about your husband that he gambles and backbites people, then he is obliged to repent to Allaah because gambling is one of the grave major sins as well as backbiting. Therefore, you should endeavour to advise him with wisdom and with soft words. In doing so, you may make use of Islamic books and tapes and seek the help of the pious and righteous people among your family, your neighbours and your relatives.
You should also supplicate Allaah as much as possible, because supplicating is a great means of achieving the good of this world and that of the Hereafter. Indeed, many people are heedless of this great means, as Allaah Says (what means): {And your Lord says, ''Call upon Me; I will respond to you.”}[Quran 40:60].
With regard to the statement of the husband "there is no benefit in performing the prayer as long as she does not obey her husband", then there is no doubt that the wife is obliged to obey her husband in what is permissible, but it is not correct to say that there is no benefit in her performing the prayer, because the prayer is the symbol of true faith and it is the pillar of religion. Also, the prayer distinguishes between belief and disbelief, between a truthful person and a liar. Neglecting the prayer is more serious than not obeying the husband.
Moreover, since you mentioned that he does not spend on his wife, then this is another sin because a husband is obliged to spend on his wife according to the text of the Quran and the Sunnah of the Prophet and the consensus of the scholars . For more benefit, please refer to Fatwa 85361.
In case the husband does not spend on his wife, then his wife is permitted to take from his money without his permission according to her need and her children's need. If she is unable to do so, she may take the matter to an Islamic court so that the judge will oblige him to spend on his wife, and if again she is unable to do so, she may invalidate the marriage contract.
For more benefit on the rights of spouses towards each other, please refer to Fatwa 85308.