What are the consequences for a young man who committed fornication with a non-Muslim woman, resulting in her becoming pregnant and giving birth to a child? And is he obligated to marry her and raise his son, or not?

You must sincerely repent to Allah Almighty from adultery. It is permissible for you to marry the adulteress if she is a Woman of the Book and she also repents, but it is better not to marry her. It is not permissible to marry her if she is not a Woman of the Book or has not repented. The child resulting from adultery is attributed to his mother, and you have no legal relationship with him as a father.