On the first point, all I could say is that the scriptural pattern is not a short one. To function as a local assembly, it may be easy for a group of Christians to do so, but the pattern description is not that simple. That is to say that the pattern is simple, but not the description of it. That is why we have about 28 epistles, four Gospels that deal with the life and teachings of Christ to His disciples, and at least one historical book. Therefore, if you are asking about the scriptural pattern of a local assembly, then it is detailed in those books. One has to learn it from those 27 books. Then only, it will be scriptural. If you learn from the writings of men, then it may or may not be scriptural. Most probably, it will be that of that man’s.
About the second point as you explained: If the assembly comes to realize the need to have an assembly at another location, because God has called out some from that locality as the result of the work done there, then that should be done as early as possible. This is the scriptural pattern, and that is how the assemblies at Antioch, Rome, Corinth, Galatia, Ephesus, Philippi, Thessalonica, Smyrna, Philadelphia, Laodicea, etc. came into existence. The members of the newly formed assembly should be taught in the Scriptural principles by those who labored from the former assembly, or as desired by them.