Question

Hello, honorable Rabbi. 
 
When a person wants to repent, but is prevented from making full repentance because of circumstances resulting from the sin, are his previous sins forgiven, so that from now on he is judged only for his new sins? Or perhaps, since his previous sins are also causing the present ones, his repentance is not considered repentance at all? 
 
I connect this question to the interesting issue of whether repentance is effective for the children of Noah or not. 
Because one of the commentators wrote that since the children of Noah are obligated only in the 7 commandments, they have no ability at all to atone for their sin. Since the 7 commandments are all in the category of passive omission, the past transgression ultimately remains on the books even if they currently regret it.
And it seems that repentance helps only if you have "settled the account" with the Holy One, blessed be He—that your creation turns out to have been more beneficial than harmful. Then that same commentator adds that if that Noahide truly corrected himself through very positive deeds, like Naaman, or converted, like Nevuzaradan, then repentance does help him as well. 
 
But what about a case where a person sinned gravely, and now is already weak, exhausted, and deeply depressed, or physically ill, and even if he repents he will not, for example, be able to become a Torah scholar, or bring merit to the public, while at the time when he sinned he caused the public to sin?
And what is the status of a person who was mentally coerced, or because of surrounding circumstances came close to sin—like a child who grew up, for example, among the gentiles, became Christian, and only in adulthood discovered the truth of Judaism—and now repents, but does not know how to study halakhic concepts, or even the Hebrew language. And perhaps his modes of understanding faith in divine unity have already become distorted, and as a result of his past he may even now arrive at flawed mental images—such as believing in the Holy One, blessed be He, as having form and image. Will his sins be erased for him even though he has come to observe Torah, or are his sins included together with his new sins? 
What about a person who sinned because of psychological causes, such as a woman who was raped, or a child who underwent physical abuse, or because of a distorted personality that became mentally ill due to excessive stringencies in the way he was educated to observe the laws?
And in general, is repentance preferable in every situation? Because if a person recognizes the Master of the universe but on his own terms and according to his own feelings—doesn't repentance in such a case only add sin to crime? (Like many who say they became religious because they discovered that religion is beautiful and not ugly. Seemingly that is not repentance, because it is an open admission that they are not willing to accept His kingship unless it suits them well.)