So how do we address the fact that historical materialism is unfalsifiable, and therefore inherently unscientific?

Historical anything is unscientific because you can't experiment on the past. The closest you can get to scientific history is to test different historical methods against each other.

It's also largely right, unfortunately.

I'm not postulating great man theory. I'm not suggesting that individuals are the driving force of history. They are the products of their times and their environments, which are themselves controlled by other forces. That being said the actions of individuals (not even "Great Men" per say, but humans in general) do influence the direction which history will take, and we can never really claim to know why an individual did what they did. Human reaction to stimuli will be influenced by their environment, what we can't say for sure is what aspect of their environment motivates them to act in a certain way, whether it was ideology or economic interest.

I suppose what I'm saying is that even if people are the product of their evironment, they still have to act and react to their circumstances in a certain way, and we have no way of knowing exactly why they might react in one way or another.

I still subscribe to dialectical materialism, however I will have to admit that it isn't scientific.

that's why its a science bro, it describes human history and predicts historical futures.

it is falsifiable if you can prove that its predictions are false, that its foundations are false, basically by falsifying it.

why do you think it is not falsifiable?

But how can you prove that they are false? Marxism argues that human behaviour is driven by economic factors, and that history is the product of various groups of people acting in their economic self interest. The issue is, how do you determine if an action was preformed in service of economic self interest? How can you be sure it wasn't done for other reasons like ideology? You can never know one way or the other, so doesn't that mean that the theory is unfalsifiable?

We do not need to know how each individual will act to know how a group will act. Individuals may have choices to make, but the effects of those choices will only change reality as much as one individual physically can.

You are thinking of history at an individual level, and historical materialism does not address it in such a way. It only concerns itself with the agrigate.

This is the correct answer. Read into the historical method, folks.

I suppose then it would be possible to disprove historical materialism if you could find repeated instances of societies or major groups consciously acting against their material interests?