I'm a Christian myself, but history is full of non-Christian communities that were stable, so I'm not sure I agree with you on that.
And I'm sure such communities will be painfully aware of their limitations. In fact, if they ever come into existence every day will be a struggle against their limitations.
Security considerations will force them to expand.
I hope these things never happen, though. When I left the family farm it was with the intention of not becoming a farmer again. :(
Stable is a relative term. In such a SHTF scenario ‘stable’ could be far from what we consider ‘stable’ now.
Further if they expand and their numbers increase, there will be huge problems for them concerning power and control of their group, factions and probably infighting for control. Without the Holy Spirit guiding these people they will be doing things for all the wrong reasons and not have that Godly guidance in the midst of the largest calamity anyone’s faced since the flood. They are not equipped to deal with it. Many Christians will not be either, mentally or supply-wise.