What is the ruling on wiping the front of the head beneath the ḥijāb, and is it permissible to wipe over the ḥijāb if it was put on while in a state of purification (wudu`)?
All praise is due to Allah, and peace and blessings be upon our master the Messenger of Allah ﷺ.
It is permissible to wipe the front portion of the head (nāṣiyah) with the fingertips. It is likewise sufficient to place a wet hand over a head covering (ḥijāb), provided the moisture actually reaches the hair beneath it — if it does not, it does not suffice. A head covering is not treated in the same manner as leather socks (khuff) and may not be wiped over in lieu of the head itself.
Imām al-Nawawī, may Allah have mercy upon him, states in al-Majmūʿ (Vol.1/P.407): "If a person is wearing a turban and does not wish to remove it — whether for a valid reason or otherwise — he should wipe the entire front portion of the head... The same ruling applies to whatever a woman wears on her head. If, however, he confines himself to wiping over the turban without wiping any part of the head itself, this does not suffice — and there is no disagreement among us on this point." He further states: "A woman is like a man in the manner of wiping the head... She should insert her hand beneath her head covering so that the wiping falls upon the hair itself. If she places her wet hand over her head covering, our scholars stated: if the moisture does not reach the hair, it does not suffice her." And Allah the Almighty knows best.
I`m a pious Muslim woman, but my husband isn`t, what should I do?
You should exercise patience, make supplication that Allah guides him to the straight path, and keep advising him kindly.
Is it permissible for a woman to sit with her brothers-in-law?
It is impermissible for a woman to sit with her brothers-in-law, and it is also impermissible for a person to have a Khulwa (seclusion) with his sister-in-law.
Is it valid for the 'aqīqah to be performed using the newborn child's own wealth?
All praise is due to Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
It is not permissible for the guardian to perform the 'aqīqah using the newborn child's own wealth, because the 'aqīqah is a voluntary act of giving (tabarru'), and a guardian is prohibited from making voluntary expenditures from the child's wealth. Should he do so, he becomes financially liable for what he spent. And Allah Almighty knows best.