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If your brother has a history of being rational and evidence driven, you might encourage them to spend some time lurking on /r/AcademicBiblical on Reddit. They require citations for each post or comment, so he may be frustrated if he tries to participate, especially if in the midst of a mental health crisis. But lurking would be very informative very quickly.
I was a long time participant there before leaving Reddit, and it's a great place for evidence driven discussion of the texts. Its a mix of atheists, Christians, Jews, Muslims, Norse pagans, etc. (I'm an Agnostic myself that strongly believes we're in a simulation, so it really was all sorts there.)
Might be a healthy reality check to apologist literalism, even if not necessarily disrupting a newfound theological inclination.
The nice things about a rabbit hole is that while not always, it's often the case that someone else has traveled down whatever one you aren't up for descending into.
(Though I will say in its defense, that particular field is way more interesting than you'd ever think if you never engaged with the material through an academic lens. There's a lot of very helpful lessons in critical analysis wrapped up in the field given the strong anchoring and survivorship biases and how that's handled both responsibly and irresponsibly by different camps.)