Shalom Tag,
I very much appreciate your words on the keeping of the Sabbath day. I've studied this alot, as I want to please God with my life and do whatever He wants. Some people get very upset and will condemn others over this issue, but I find that the apostle Paul summed it up this way:
Romans 14:5 One man esteemeth one day above another: another esteemeth every day alike. Let every man be fully persuaded in his own mind.
6 He that regardeth the day, regardeth it unto the Lord; and he that regardeth not the day, to the Lord he doth not regard it. He that eateth, eateth to the Lord, for he giveth God thanks; and he that eateth not, to the Lord he eateth not, and giveth God thanks.
There has been much heresy in the Gentile church about the law not being kept, and I do think that in the end time days many will be surprised for not having kept it in their hearts. Along with the verses about law, though, it is good to say that love is the fulfilling of it, or that the spirit of torah is love. Nobody would break any laws if they truly loved as the scriptures say, repeatedly. The law is the greatest teacher mankind has ever had that was written down for us by God and it is FULFILLED - not done away with as you said.
Ro 13:8 Owe no man any thing, but to love one another: for he that loveth another hath fulfilled the law.
9 For this, Thou shalt not commit adultery, Thou shalt not kill, Thou shalt not steal, Thou shalt not bear false witness, Thou shalt not covet; and if there be any other commandment, it is briefly comprehended in this saying, namely, Thou shalt love thy neighbour as thyself.
10 Love worketh no ill to his neighbour: therefore love is the fulfilling of the law.
Mt 22:35 Then one of them, which was a lawyer, asked him a question, tempting him, and saying,
36 Master, which is the great commandment in the law?
37 Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind.
38 This is the first and great commandment.
39 And the second is like unto it, Thou shalt love thy neighbour as thyself.
40 On these two commandments hang all the law and the prophets.
The only part of the law abolished would be the ordinances, and perhaps you could tell me exactly what they were? My guess would be blood sacrifices and activities that took place at the temple and Holy of Holys.
Ephesians 2:13 But now in Christ Jesus ye who sometimes were far off are made nigh by the blood of Christ.
14 ¶ For he is our peace, who hath made both one, and hath broken down the middle wall of partition between us;
15 Having abolished in his flesh the enmity, even the law of commandments contained in ordinances; for to make in himself of twain one new man, so making peace;
16 And that he might reconcile both unto God in one body by the cross, having slain the enmity thereby:
I also see the verse you gave in Revelations about those "which keep His commandments and have the testimony of Jesus Christ" as interesting and fitting with the verses in Romans 14. The two houses of modern day Israel will come from different backgrounds - having been brought up to observe different days. I believe that Ephraim and Judah are to unite in the last days to fight the beast, as Zechariah says that Ephraim will be the arrow to Judah's bow. Ephraim would be the Gentile church, and Judah the Messianic believers in Yeshua - both having one Saviour, but very different backgrounds and upbringing. Nevertheless they will have a brothers love for each other through and because of Yeshua.
Also, the verse in Matthew has something else that is interesting to consider, for it says "until all things are accomplished". My King James version says "till all be fulfilled". Now accomplished would lean towards what you said later - that surely heaven and earth haven't passed away, but fulfilled would lean more to the work that Jesus did on the cross and the fulfillment that happened when He said "it is finished", bowed His head and gave up the ghost. At that moment, the veil of the temple was rent in twain from top to bottom.
Look at the apostles - they went to Synagogue on Saturday to teach the Jews about Jesus. However, when they gathered as Christians they did so on the day of the Resurrection - the 8th day. 
