Should one fulfill a vow by slaughtering an animal, or continue paying the installments for the house, knowing that the questioner is committed to paying a monthly amount, and that he vowed to slaughter an animal if his wife recovered, and she has recovered, and that his financial circumstances were difficult and he was forced to buy a house with a loan?

If the vow is specified for a certain time, it must be fulfilled on time, unless you are unable. If it has no specific time, it must be fulfilled gradually, with the recommendation to hasten. If you can combine paying installments and fulfilling the vow, then do so. Otherwise, prioritize paying installments if they have a specific time, because people's rights are based on exactingness, and Allah's right is based on leniency. A conditional vow is disliked, but it must be fulfilled.