All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
You have done well by preserving your religion and being firm on your principles. We ask Allaah to reward you and preserve you and your religion. It should be noted that a Muslim is required by the Sharee‘ah to be firm on Islam and it is forbidden for him to flatter the unbelievers. Allaah The Almighty Says (what means): {And if We had not strengthened you, you would have almost inclined to them a little. Then [if you had], We would have made you taste double [punishment in] life and double [punishment after] death. Then you would not find for yourself against Us a helper.}[Quran 17:74-75] So, it is forbidden for the Muslim to participate with the people of falsehood in their falsehood even if they are Muslims, let alone if they are unbelievers. Talking about His faithful slaves, Allaah The Almighty Says (what means): {And [they are] those who do not testify to falsehood, and when they pass near ill speech, they pass by with dignity.}[Quran 25:72]
In fact, the Muslim's steadfastness on his principles is one of the major elements which help present the best image of a Muslim and Islam in people's eyes while the pleasure of people with his flattery will not last for long. On the contrary, they may depict the flatterer as a hypocrite. Therefore, you have to remain steadfast on the truth, and when the matters go as far as choosing between loss of religion and loss of the worldly life, loss of the worldly life is easier. Allaah The Almighty Says (what means): {Say, "The enjoyment of this world is little, and the Hereafter is better for he who fears Allaah."}[Quran 4:77] Surely, a Muslim who gives up something seeking the pleasure of Allaah The Almighty, He will compensate him with another better thing. Allaah The Almighty Says (what means): {And whoever fears Allaah - He Will Make for him a way out. And Will provide for him from where he does not expect.}[Quran 65:2-3] The Prophet, sallallaahu ‘alayhi wa sallam, said: "You will never leave something for fear of Allaah The Almighty, but He will compensate you with a better thing." [Ahmad]
As for attending these classes, there is no harm to attend the classes which are not based on matters that contradict the Sharee‘ah, such as the examples you mentioned above. However, it is not permissible to attend the classes which are connected to those people’s false creed or accompanied by doing any of their rituals of disbelief even if this would result in the employee getting fired from his job. For further information about Buddhism, see Fatwa 107137.
Allaah Knows best.