Great; these two things are seemingly inconsistent. Which means one must be false. But if either of these is false, it's surprising! Because one is based on our direct experience of ourselves, as you have pointed out, and the other is based on well-established science. So what's interesting about Boltzmann brain (and similar) is that it shows that one part of our body of knowledge must be false. And this ought to motivate us to investigate exactly what it is that we have wrong.
What I want to know is this: will BBs exist in the immeasurably far future? If they will exist, how fast could they possibly think, how long could they last, and what is the limit on their intelligence? Could they comprehend their own existence from first principles? In the short instants that they exist, would they realize how short their life expectancy is?
>Two - based on well-accepted science - is that it is MUCH more likely for you to be a boltzmann brain than not.
We're not each individual BBs (and you're not a lonely BB imagining the rest of us). It's closer to the truth that our entire universe is one big BB that just blipped into existence one moment billions of years ago. If we accept the concept of a Boltzmann Brain at all, then it must be that some configurations of one where parts of the brain are disconnected from each other and each spawns and intelligence... or even just unintelligent matter/machinery. Scale that up to a few billion light years wide, and that's us.
And if you were a BB, you probably wouldn't know it, and how you experience yourself is irrelevant. That's kinda the point. The problem with the BB thought experiment is that it isn't falsifiable, at least not with techniques we have now.
The problem is that if you start with the reasonable assumption that you objectively exist and that your observations are valid, the model of the universe derived from those observations (or at least some otherwise viable models) includes prevalence of Boltzmann brains.