I do not understand why you are quoting these verses, which in themselves are very useful, but have nothing to do with Paul assuming the authority to discontinue circumcision.
Paul isn't assuming authority
God is referring to the Sinai covenant and adding understanding.
No God isn't referring to the Sinia covenant. THE FACT you don't see that should give you great pause. It is A New covenant which the Lord is making with Israel in Moab prior to entering into the promised land. This Covenant is in addition to, or beside the one made in Horeb which is Sinai. In this one the Lord does the circumcising not us. And that circumcision is of the Heart not the flesh. Take note in Deut 10:16 where God tells the people to circumcise their hearts for the first time. But in Deut 30 God says for the first time He will do it. He will put His commandments, statutes contained in the Book of the Law in our hearts that we do them. This changed heart through God is actually the circumcision which He speaks of in verse 6. God through Paul Paraphrases these verses from Det.30:10-14 in Rom 10:6-8. It is the culmination of the Book of Romans actually.
Deut 10:16 Circumcise therefore the foreskin of your heart, and be no more stiffnecked.
Deut 30:6 And the LORD thy God will circumcise thine heart, and the heart of thy seed, to love the LORD thy God with all thine heart, and with all thy soul, that thou mayest live.
Deut 29:1 (NET) These are the words of the covenant that the LORD commanded Moses to make with the people of Israel in the land of Moab, in addition to the covenant he had made with them at Horeb.
Deut 29:1 These are the words of the covenant, which the LORD commanded Moses to make with the children of Israel in the land of Moab, beside the covenant which he made with them in Horeb.
Deut 30:6 And the LORD thy God will circumcise thine heart, and the heart of thy seed, to love the LORD thy God with all thine heart, and with all thy soul, that thou mayest live.
Deut 30:10 If thou shalt hearken unto the voice of the LORD thy God, to keep his commandments and his statutes which are written in this book of the law, and if thou turn unto the LORD thy God with all thine heart, and with all thy soul.
Deut 30:11 For this commandment which I command thee this day, it is not hidden from thee, neither is it far off.
Deut 30:12 It is not in heaven, that thou shouldest say, Who shall go up for us to heaven, and bring it unto us, that we may hear it, and do it?
Deut 30:13 Neither is it beyond the sea, that thou shouldest say, Who shall go over the sea for us, and bring it unto us, that we may hear it, and do it?
Deut 30:14 But the word is very nigh unto thee, in thy mouth, and in thy heart, that thou mayest do it.
Rom 10:6 But the righteousness which is of faith speaketh on this wise, Say not in thine heart, Who shall ascend into heaven? (that is, to bring Christ down from above
Rom 10:7 Or, Who shall descend into the deep? (that is, to bring up Christ again from the dead.)
Rom 10:8 But what saith it? The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach;
The English words are choices made by translators and with word for word translations, like the KJV, the words chosen by the translators, reflect their personal opinion, and can only be approximately equivalent anyway. Let us look at some different translations.
The word for Circumcision is translated properly. Grab a Strong's concordance you will see ever occurrence. There are not many.