Is returning to Egypt and leaving a prestigious job in Saudi Arabia considered a form of ingratitude for Allah's blessings and a lack of contentment with His divine decree, especially since the employers wish for me to stay?

Your decision regarding your job is a personal matter; whether you stay or leave, there is no sin upon you, nor is there any blame according to Sharia. Your leaving your job and returning to your country is not a sign of ingratitude for blessings. We advise you to perform Istikhara, which is a supplication that includes acknowledging the existence of Allah and His attributes, entrusting matters to Him, relying upon Him, and seeking good in what concerns you, as the Prophet, peace and blessings be upon him, said: "O Allah, I seek Your guidance by Your knowledge..." It is among the causes of happiness and contentment with Allah's decree.