“the Church” cannot revoke the principles God has set, hence calling it “Noahide Law” and making a leap from that to,
“We are saved by grace alone and not by the works of the law.” is unwarranted and misses the whole purpose of God’s pronouncement on the restriction on blood use.
Those “necessary things” are still necessary in obedience to the Scriptural principles.
“the Church” could no more drop restrictions on blood than fornication.
Sure she could, and she did. The restriction on blood is different from the restriction on fornication, because no one is hurt by eating blood any more than by eating steak (Shakespeare's Merhcant of Venice story comes to mind). Fornication though is in itself inflicting damage on people.
Divine revelation is progressive. God reveled Himself to the primitive people in simple Don't's like "don't drink blood" because they were primitive -- we do the same thing when we tell children not to run with scissors. The Revelation God gave the Christians is Love God and love your neighbor, and about the rest think for yourself -- you are not saved by the laws but by your works.