Valid questions you ask. The one I believe I can answer is the reason we as fallen creatures have managed in 2000 years to take one unified church in Acts and managed to turn it into hundreds of denominations and thousands of subgroups is our sin nature and self serving approach to life.  Someone says, "I do not want instruments in the worship service, lets start a denomination."  I think the congregation should rule the church, lets start a denomination.  I found two gold leafs, lets start a denomination.  The Bible teaches to sprinkle infants before salvation.  Lets start several denominations.  One must be baptized to be saved.  Lets start a denomination, etc, etc, etc,.  If you believe that one can lose their salvation, then the HS in you guided you in a different direction that me.  You must listen to and be guide by Him.  The example I gave you is how I was guided by the HS and can only offer I as an example.  It is more of reading the Bible, praying, and being guided by the HS than it is analyzing 100s of different groups.  Go where the Lord leads you.