Good post for sure. I can chime in from the environmental consulting and remediation side. Honestly, from the pictures that doesn’t look that bad. If it were my house I’d treat with biocide, paint, and be done with it assuming it’s fully dry and the water problem is gone.
Not an official recommendation of course, but I wouldn’t use bleach. Bleach can damage building materials. What’s a better option is something like Shockwave or Concrobium, something that is EPA-registered for use as a biocide. I would apply it on both sides of the drywall to the point of it soaking in, and then allow it to get fully dry. After I was SURE it was dry I’d paint both sides with Kilz primer, and repaint to suit. The Kilz primer will act as an encapsulent and make sure you are not exposed to any of the dead mold.
I’ve done quite a bit of mold removal in my house from before we encapsulated the crawl space, and this has worked flawlessly even though I have family members that are extremely sensitive to molds. I wouldnt worry too much about mold spores present throughout your house- the dirty secret of the remediation industry is that there are mold spores literally everywhere. They key is to make sure the humidity levels in your house are controlled and never exceed 60-65%.