Is it incumbent on a family to provide for its old handicapped son and take care of him?
The family and relatives - e.g. brothers - of such a person are obliged to spend on him and take care of him if he didn`t have money of his own.
Is it permissible for the wife to give the Zakah (obligatory charity) of her money to her poor husband?
Yes, it is permissible for the wife to give from the Zakah of her money to her poor husband. And Allah Knows Best.
If someone unknowingly bought stolen cement multiple times, and if the seller is revealed, will my husband bear any sin?
The sin of the theft falls on the one who stole. However, the person who used the cement must pay its value to the rightful owner from whom it was stolen, and then seek reimbursement from the seller. If the thief compensates the rightful owner, there is no liability on the person who used the cement. And Allah Almighty Knows Best.
Is the one who doesn`t offer prostration of recitation during Quranic recital considered sinful?
Prostration of Quranic recital is a Sunnah due on whosoever recites a verse that contains a prostration. It is also a Sunnah for the reader and the listener. However, none of them is considered sinful for not offering it, but they deprive themselves from a great reward. It is obligatory to offer the prostration of Quranic recital in congregational prayer following the lead of the Imam.