Should the husband be prevented from sending money to his family monthly until the loan is paid off, given that he considers loans a normal matter for life's necessities in Europe?

If the husband provides for his family and regularly pays off loan installments, then there is no blame upon him for assisting his family with his money, and the wife has no right to prevent him. However, if he falls short in providing the obligatory maintenance or in paying off the loan, and instead donates his money to his family, then the wife has the right to demand that he provide for them, and to advise him to pay off the loan installments first, because that takes precedence over donations, as stated in the hadith: "No charity is valid except when one has sufficient means, and the upper hand is better than the lower hand, and begin with those whom you support." Usurious loans are among the major sins and are not permissible except in cases of necessity or dire need.