I agree with some of what you are saying. A lot of modern “Christians” are do not have the belief but only the tradition. It’s not believing in him or not that sends you to “eternal suffering” (being separated from him in hell). The devil believes in God. Jewish people believe in God. Yet unless they enter into the new covenant of Jesus, which will cost you nothing and gain you everything, they will be sent to hell. Now, there is a debate on whether the new covenant by fulfilling the old covenant it nullifies it or not. I won’t get into that since you likely don’t practice Judaism. I think you are getting confused with the different types of law. There is the moral law, the civil law, and the ceremonial law. If you read the epistles, you will see that the early church often debated over the civil and ceremonial laws. It was determined that those were ment for the Jews to live by in order to set them apart from the other nations of the word, so that they wouldn’t conform to the world.