All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
There is evidence from Sharee'ah texts that Ihsaan (doing good) is required from a Muslim and that he gets reward (from Allaah) for being good to everything, and animals are included in this. The Prophet said: "There is a reward (for you) in every creature with a moist liver [i.e. every live animal]." [Al-Bukhari and Muslim] Besides, the Prophet said: "Verily, Allaah has prescribed Al-Ihsaan (doing good) to everything.” [Muslim] For more benefit, please refer to Fatwa 83830.
Therefore, feeding these cats is an act of charity and an act by which one gets closer to Allaah especially if they are hungry and did not find food to eat. Nonetheless, cats can eat from the pasture of the earth, so instead of buying food for them with that money, it is more appropriate for your husband to spend it on feeding poor people and if there are no poor people in your country, then there are many poor people in Muslim countries who need food, drink and clothing. Indeed, he may send it to them through trustworthy charity organizations.
As regards obeying your husband in feeding cats, then you are not obligated to do so especially that you are scared of them and harmed by them. The jurists stated that a wife is obligated to obey her husband regarding marital life and matters that are related to it; for more benefit, please refer to Fataawa 91208 and 91788.
Allaah Knows best.