Is the husband's work that necessitates intermingling with women considered a legal necessity, and what is the ruling on the money earned from it? And must the wife encourage her husband to remain in a place free from intermingling to ensure lawful earnings?

We ask Allah to reward you both with goodness and increase you in guidance.

If the mixing is forbidden, meaning it does not adhere to the manners of Islam, then it is not permissible to work unless out of necessity, such as the absence of any other work to earn a living. In this case, one may continue while taking precautions, such as lowering the gaze.

However, if the mixing is merely a gathering with adherence to the rulings of Islamic law, without seclusion (khalwa) or immodest display (tabarruj), then it is not forbidden.

The money earned from this job is permissible (halal) if the work itself is originally permissible. Mere mixing does not prohibit the wages.

There is no blame on your husband for traveling for permissible work if he is secure from temptation, especially given the instability of his current job.

You are not obliged to encourage him to reside in the aforementioned country. However, if he insists, then you must reside where your husband resides, unless there is a legitimate Islamic impediment.