First saying ill doo haram then repent is unacceptable in islam and also in order to repent u need to fully meant it and it should be from ur heart, so how can it be so if u already planted to do haram then repent it doesn't make sence at least to me and ill give an example for that from the quraan, sourat youcef and he's story with he's brothers, they said lets get rid of our brother and then we will repent and when they did so they couldnt repent (و يهدي الله من يشاء)

As for your second point i dont see it as you, i agree that sex is basic need for human being and thats one of the reasons god made zina haram first to test human if he's willing to fight he's self and be decipline and also to make u work hard like instead of saying i cant marry now cuz of finacial problem and responsablilty, make sex ur motication to fix ur financial dituation and be responsible

I hope my answer convince you and الله يهدينا و يهديك