Must a fiancé be frank with his fiancée about his past suffering from masturbation addiction and its resultant symptoms, and could these symptoms affect marital life or cause injustice to the wife?

Masturbation is forbidden, and it entails negative consequences. You must conceal yourself and not inform anyone of this sin, for the Messenger of Allah, peace and blessings be upon him, said: "Avoid these foul deeds that Allah has forbidden. Whoever commits one, let him conceal himself with Allah's concealment and repent to Allah." Hasten to marry in obedience to the command of the Prophet, peace and blessings be upon him, and do not tell the woman you intend to marry anything about this. If some illnesses appear on you, you may consult a specialist doctor.