A couple of things:
1) In my experience, chlorinated brake cleaner is fairly uncommon, even in jurisdictions that still allow its sale and use. Most of the stuff I grab off the shelf at the local parts store is non-chlorinated/low-VOC formulation (and no, I don't live in California or some other state that mandates this stuff).
2) Excessively heating chlorinated compounds can indeed be very dangerous. Don't do that. Keep the stuff away from spacer heaters and open flames, and makes sure a part is completely dry before exposing it to high heat. Avoid the stuff for welding in general. At normal room temperatures, the stuff evaporates pretty quickly and I've got very little concern about the health hazard of using it to clean a firearm. If you hose down the interior of a suppressor or similar component in cooler weather, it may stick around for many minutes and so plan accordingly.
3) As far as "drying the pores" of metal is concerned, solvents do indeed break down and remove oils. That's basically the point of using them! And if the metal is quite cold - like well below normal room temperature - a solvent can stick around long enough to disturb a fresh application of oil or paint. I've seen this before when working in an unheated shop during winter. In this case, make sure the solvent is completely evaporated by applying some compressed air, or have some patience. High-quality gun parts of the type we are considering here do not have "pores" that are going to open up, trap solvent, close up, and then wait patiently to destroy lubrication at a later time. Sintered self-lubricated bearings are a different story, and if your firearm contains such a part, act accordingly. I've also gotten screwed by cranks and what-not in porous castings when attempting to clean the surface and apply paint, but if this applies to someone's firearm, lubrication failures are likely low on the list of future problems.
Apply solvent, dry solvent, apply lube, and get on with life. The deeper the cleaning process, the more work required to reapply lubrication.