Is it obligatory for a young man to return to his home country due to his inability to marry in a non-Muslim country, especially given the presence of mosques and Muslims, and limited job opportunities in his home country?

If a Muslim is confident in being able to practice his religious rites and avoid fitan (trials/temptations) in a disbelieving country, then there is no impediment to his staying there to complete his studies until circumstances for work become easy for him to return to his country, and marriage is more appropriate for him.