Is it permissible to be absent from attending two congregational prayers in the mosque due to being occupied with another job, and is the salary considered "haram" as a result, knowing that there is a disparity in salaries between officially appointed imams and those not officially appointed for the same tasks and competence?

The Imam must adhere to the contract and its stipulations. Therefore, it is not permissible for him to be absent from his mosque except for a valid excuse, or with permission from the responsible authority, or as is customary. A low salary does not permit him to be absent or to violate the contract. Scholars have forbidden the Imam's absence without an excuse or permission, and they have forbidden him from receiving his salary in exchange for his absence.