Is the questioner considered sinful for the illicit relationships he had in the past, and does the principle of "what goes around comes around" apply to him, which might affect his daughter?

The transgressor's concern about worldly punishment prevents him from repenting. However, sincere repentance erases the effects of sins in this world and the hereafter, and restores the servant as if he had never sinned. It involves great acts of worship and humility before Allah, and is more deserving of effacing the effects of disobedience than effacing the effects of disbelief. The Prophet, peace and blessings be upon him, said: "The one who repents from sin is like one who has no sin." The transgressor must hasten to repent by feeling remorse, abandoning the sin, resolving not to return to it, and increasing acts of seeking forgiveness and doing good deeds. If Allah accepts his repentance, He will overlook the effects of his sin in this world and the hereafter.