Can people's livelihoods be affected by magic such that they are unable to save money, and is it possible that the questioner's uncle had a hand in that through the use of a book of incantations?

Magic can affect financial, psychological, and health aspects, but sustenance and lifespan are predetermined, and no one can withhold sustenance or delay one's lifespan. Allah has guaranteed every soul its sustenance and its lifespan, and a person does not leave this world until they have fully received both. Believing in the existence of magic to hinder sustenance, or inventing a special ruqyah (definition) (exorcism) to undo it, indicates a weakness in reliance on Allah and conviction, and is an innovation in religion. For whoever fears Allah, He will make a way out for him and provide for him from where he does not expect. A sorcerer may cause people to lose their wealth, but a lack of barakah (blessing) in wealth does not necessarily mean there is magic; it could be due to sins, cutting off kinship ties, and extravagance. It is not permissible to believe those who deal with jinn when they accuse a relative of practicing magic, as this is considered fisq (transgression) and ill-suspicion. Moreover, Islamic law forbids anything that causes enmity among Muslims. Kinship ties must be maintained even if they are severed by others, for upholding kinship ties is a cause for attracting sustenance and blessing therein. Part of perfecting kindness to the uncle is to advise him to abandon magic and destroy his books.