I'll cross-post my answer, so we can have an answer to your question here as well.
Our policy on parenting.se is "opinions shared here should be backed up either with a reference, or experiences that happened to you personally".
In practice, this rule is not referenced very often. It occasionally comes up when an extreme stance or blanket statement is made without any obvious or intuitive support (e.g. "all kids study harder when they play soccer every week"), and is usually more to reign in topics that seem to be getting derailed into subjective personal opinion.
We also have a second policy that is closely tied with the reference or personal experience rule: "posts that primarily exist to push a specific agenda (propaganda), and soap-boxing, are not welcome".
This one gets cited a bit more frequently, and is used to put the brakes onto any topic that is in serious danger of turning into a full-blown argument.
I think the second policy would be of less use to your site, since your proposal of sticking within the context of a specific tradition should serve a similar purpose, and possibly more effectively.
For the first policy, perhaps you could extend it to "you must provide a specific example from where your experiences to support your advice"? This type of rule would be problematic on parenting, due to the sheer volume of hypothetical and subjective issues, but since this seems to be a small subset on Christiantiy.se, perhaps some variation of it would work for you.
One thing to keep in mind is that by allowing these types of questions, even with specific provisions and restrictions, you may find that it will be fairly common for people to miss those provisions and restrictions. Many of those will likely provide quality content, though. I would suggest that you go into it with the understanding that the rules would be enforced when things got out of hand, rather than for every instance, simply because not everyone will research the specific topics on meta, or even your faq, before posting.