What is the Shariah ruling on not fulfilling a vow made to Allah to sacrifice a calf for the poor, and what should be done to alleviate difficult circumstances and straitened provisions, which might be caused by not fulfilling this vow?

One must fulfill their covenant with Allah, and this promise is considered a vow that necessitates fulfillment. If the questioner is unable to fulfill their covenant, they must offer expiation for breaking an oath. As for resorting to sorcerers, it is forbidden. One must repent, seek forgiveness, and seek Allah Almighty's help, for tribulation descends due to sins. The weapon of the believer is supplication and recourse to Allah Almighty.