The Whore of Babylon is the Catholic Church. The Apostle John was astonished because the woman looked like Mary, the Lord's mother.
The Jewish Law with it's 613 commands is no longer in effect. That should be obvious.
God isn't looking for "remnant people". That phrase is not found in the Bible. Believers became known as "Christians". That's what believers should be called.
To be saved you need to repent of your sins. Accept what Jesus did on the cross as payment for those sins. Accept Jesus as Lord. Salvation is like a gift. You can know it's available but until you consciously accept it, it isn't yours. If Jesus is your Lord you'll do the best you can to live a holy life and do the things the Bible commands.
If you want to grow as a Christian you should pray everyday (I use the ACTS model of adoration, confession, supplication, and thanksgiving), read the Bible everyday and go to church regularly.
Revelation 12:17 is an example where "remnant" is mentioned.
Jesus did not come to abolish the law, but to fulfill it (Matthew 5:17).
Nowhere in the Bible does it say that the Law has been done away with. Yes, we are saved by grace through faith, but that does not mean that we should no longer strive to keep God's commandments.