Jewish law is what you are referencing and then trying to make a circular argument to include orthodoxy and that isn't accurate. You are talking about juudaizers who wanted to make circumcision a requirement. I had this argument with last's nights protestant too. It's like deja vu.
I am talking about the earliest years of the church. Run by the people whose books you read. Matthew, Mark, Luke, John, Paul, etc. All saints BTW. If the book of John says you have no life in you without consuming the body and blood, then yes, I would take that as the same level of commandment as Christ saying "love your neighbor". It is part of the saving process. Notice I didn't use "saved" in past tense.