Realistically, can extreme, chronic stress for 6+ months cause bacterial pneumonia in someone who is otherwise healthy, no risk factors, and who did not have a preceding viral infection? trying to make sense of what happened to me?

In theory, stress might have effects on the immune system that could increase pneumonia risk, but there is no solid scientific evidence for it. Most likely your pneumonia was not related to your stress situation, but there is simply no way to know whether these two things are related in any particular case or just a coincidence. Probably it's a coincidence.