Is what I am doing—erasing numbers and offensive, abusive words from walls, as well as reporting shops that sell Christian symbols or unclean restaurants—a correct and legitimate act, or is there something more important than that, taking into account the fear of cutting off their livelihoods when reporting them?

Enjoining good and forbidding evil is one of the rituals of Islam and a reason for the goodness of the Ummah. It is a collective obligation (fard kifayah) and may become an individual obligation for one who is capable. Erasing obscene language is a way of changing evil. Informing the competent authorities about evil deeds is obligatory if advice is not heeded and if no harm befalls the informant. Concealing a Muslim's fault is permissible if he is not known for corruption, and advice must be given with it. If he does not repent, it is permissible to refer his matter to the authorities. However, if the evil act is continuous or its perpetrator is known for corruption, there is no concealment for him; rather, it is obligatory to condemn it and refer it to the ruler (wali al-amr) if no greater harm results.