Does thinking about past sins and reliving them, despite seeking forgiveness, restraining oneself, and remembering repentance, indicate a flaw in one's repentance and render it less than sincere?

Remembering a sin does not invalidate repentance. Indeed, it is commendable if accompanied by brokenness, remorse, and seeking forgiveness. However, one must be cautious that remembering it does not lead to longing for the sin. Therefore, it is necessary to forget it or feign forgetfulness and cease thinking about it. If the remembrance of the sin becomes overwhelming, let it be a starting point for correcting and renewing sincere repentance through seeking forgiveness and performing righteous deeds. Among the things that help in forgetting a sin are: abandoning places of disobedience, associating with the righteous, and engaging in acts of obedience.

As for salary, zakat is not obligatory on it until it reaches the nisab and a hawl (one lunar year) passes over it. The nisab is equivalent to 85 grams of gold. The questioner is advised of the obligation not to deal with usurious banks. If compelled to deposit money in a usurious bank, it should be in a current account.