Dietary dispensation and omission of circumcision come from +Paul. Clearly, this was necessary to make the faith more acceptable to Gentiles. Ironically, the Church then imposed its own dietary restrictions over time, somuch so that today Orthodox Christians fast just about 180 of 364 days a year! Orthodox fast, ideally, means one meal a day, no oil or meat or any animal product of any kind (i.e. milk, cheese, eggs, etc. -- even jello because it is derived from bones). Every Wednesday and Friday, various feasts, 40 days before Nativity and 40 days (strictest fast) during Great Lent, or Great Fast, before Resurrection.
+Paul clearly states that we are not under the Law but under Grace. Although Christ never taught that, Pauline teaching became the norm even though he himself admits that he is not commanded by the Lord, but gives judgemnt on his own accord, as a his servant.
Hm, not quite. St. Paul wrote about circumcision, but the lifting of the dietetic law and the circumcision requirement was the initiative of St. Peter (who had a vision about the abolition of the dietetic law) and confirmed by St. James (Acts 15).
Pauline teaching became the norm even though he himself admits that he is not commanded by the Lord
You are not suggesting that there is a dissonance between the teaching of St. Paul and Christ, are you? Paul taught that the works of Jewish law specifically, or by extension, works of any law, do not save absent faith, which comes from grace. But one who believes is still subject to the law of the Church, and risks his salvation if he disobeys it.
"+Paul clearly states that we are not under the Law but under Grace. Although Christ never taught that..."
Well, that's not quite true. For example, Christ repeatedly "broke the Sabbath." He even used a specific example of David eating something he wasn't supposed to eat (the blessed bread in the tabernacle of the Lord) to illustrate his point that "the Sabbath was made for man, and not man for the Sabbath."
Given the centrality of Sabbath-keeping in the law, this alone was a huge statement by Christ regarding the law.
You are right that the Church ended up setting dietary restrictions, and I suppose that there is some irony in this, but in the Christian era they have a different character, a different motivation, and a different goal.
In the Old Testament, God was teaching a basic concept of "clean" and "unclean" -- some of this may have been determined by the associations certain foods had in the pagan world, and in Egypt in particular. We don't know. Part may have been just the beginnings of teaching self-control and separateness from the pagan world in general. I don't know.
In the New Testament era, our fasting is of a positive, ascetic nature. It is also a specific and direct reaching back to Paradise, where we didn't use animals as sources of food. But as far as I know, there are no foods that are completely banned at all times (other than blood, which is specified in the New Testament as being off-limits.)
To a great extent, Orthodox fasting guidelines are a formalization of the kind of ascetic fasting that probably took place spontaneously and through the effect of oral tradition from the Apostles.
That seems to be a good summary to me. My reading of the 15th chapter of Acts is that the decision that converts to Christianity are not required to observe Old Testament law comes from the apostles (including Paul) gathered in Jerusalem:
28 For it has seemed good to the Holy Spirit and to us to lay upon you no greater burden than these necessary things: 29 that you abstain from what has been sacrificed to idols and from blood and from what is strangled and from unchastity.The quotes need to be read in context starting from Chapter 11 where Peter sees a vision of many kinds of animals and a voice tells him to kill and eat. He protests but the voice from heaven says, "What God has cleansed you must not call common."
There is a long tradition in Christianity that says Christians are not subject to the law because it has been fulfilled in Christ. That is what Christ meant when he talked about the law being fulfilled.