What has a wife to do if the husband keeps looking at porn, despite her confronting him about it, telling him how it makes her feel, and crying over it, even though he says it won’t happen again?
Should she divorce him?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

May Allah reward you, dear sister, for your keenness on abiding by Allah's limits and rejecting evil. You have to continue admonishing your husband and reminding him of Allah's punishment, hoping for his guidance and repentance.

Yet, you must not ask for divorce since this will cut off the marital bond which Allah, The Almighty, recommends to be maintained.

If he insists on committing sins and abandoning his religious duties, then, in this case, you may ask for divorce.

Imam Ibn Qudamah said:

“The summary of this issue is that if a wife is displeased with her husband's behaviour, physical attributes, old age, weakness, etc., so much so that she fears she will fail to do her duties towards Allah by obeying her husband, then, in this case, she may ask for divorce in return for compensation paid to him to ransom herself. This is based on the Saying of Allah (which means): {… But if you fear that they will not keep [within] the limits of Allah, then there is no blame upon either of them concerning that by which she ransoms herself.} [Quran 2:229] ” [End of quote]

Allah knows best.