Will a Christian who dies enter Hellfire? And is circumcision obligatory if it is painful?

Your father died as a Christian, so he is among the people of Hellfire. As for circumcision, it is from the practices of the prophets. The command for it came in the Torah, and it was distorted in the Gospel. There is no disagreement among Muslims about its permissibility, though they differed on whether it is obligatory or a Sunnah (definition). What we advise is to perform it if it does not cause harm. It has great medical benefits proven scientifically, including reducing the risk of penile and cervical cancer. We advise whoever invited you to Islam not to insist on your circumcision, as it is not a condition for the validity of Islam. If it entails harm or hardship, the request is waived. Let him present the matter to you gently and wisely until you are reassured.