Does a vow become binding by uttering aloud, "A vow for a job," without a specific intention, and then the intention to donate the salary from this job arises later? And is it obligatory to donate the salary in this case?

A vow (nadhr) is not binding unless it is made with a صيغة (formula or expression) that indicates commitment, such as saying: "It is for Allah upon me to do so-and-so," or "I have vowed so-and-so." Therefore, your statement "a job vow" is not considered a vow because it does not convey commitment. Furthermore, you did not intend it as a vow. Consequently, nothing is binding upon you. It is advisable to ignore intrusive thoughts (waswasah) and not to dwell on them.