Is it permissible for the buyer to ask the government to seize his father's money from the price of the house so that the wife does not get half of his share in the event of divorce, and only gets half of what the buyer pays?

These laws that grant the wife half of the marital home, or other properties of her husband after his death, are contrary to Islamic Sharia (definition). It is permissible to rid oneself of the injustice of this law as much as possible.

If the government's impoundment of what the father paid for the house proves his partnership to the extent of what he paid, then there is no harm. However, if the father gifted this money and did not intend partnership, then caution must be exercised to preserve the right of the owner and the heirs.