Is it permissible to return to work at the previous computer office – where transgressions used to occur – due to financial need, while leaving the current job with the meager salary?

If the work you left necessitates falling into a Sharia (definition)-forbidden act, then it is not permissible to return to it. One should be content with the current permissible work and be patient until Allah facilitates another job that fulfills one's needs. For, "The Holy Spirit breathed into my soul that no soul will die until it completes its term and receives its full sustenance. So, fear Allah and be graceful in seeking [sustenance]. Do not let the slowness of sustenance cause any of you to seek it through disobedience to Allah, for what is with Allah cannot be attained except through obedience to Him."