What is the fatwa regarding this money from which I eat, and how do I deal with myself and this inner struggle, especially since I fear that this money may be unlawful, and I notice a lack of blessing in it and a decline in my faith and eagerness for worship?

The default assumption about the wealth of Muslims is that it is lawful and earned through permissible means. It is not permissible to deviate from this principle except with definitive proof or strong probabilistic evidence. Therefore, there is no harm in benefiting from the wealth of a person whose source is unknown, and these misgivings should be abandoned.