Fascism is a stage of colonial development, when the rate of imperial superprofit began to fall and the empire came home

But this didn't actually happen! Germany was crushed under the new WW1 order, wasn't fielding an imperial colonial army abroad, and it didn't come home. It emerged from the material conditions where it was, it did not leave and come back.

In fact, all the examples of the empire turning inward that we have are not examples that people would call fascism. For example, the system in the USA called "state police", which are different from local police, was a returning of the empire to their home in that the model for the state police was the design of the USA occupation forces in The Philippines. The rise of military weapons in the hands of USA cops is a direct returning of the empire to home, yet people are still talking about the USA as if it might become fascist later.

I understand the points you're making, I just don't think they reflect history at all.

and it’s not as if fascism and colonialism are truly different things; they’re part of the same ongoing process, two sides of the imperial boomerang.

I think they aren't different things - they are the same side of the process. I don't think there is an imperial boomerang. Again, I think the entire idea of the boomerang and the idea that fascism is when fascism becomes fascism is a white liberal ideological construction and doesn't match the material reality. If the only time its fascism is when powerful white people become oppressed, then that's not a useful analysis. White people are oppressed all the time in the USA and Europe - not to anywhere near the same degree, and not systemically/structurally on the basis of their racialized grouping, but it's undeniable that there are plenty of white people under the boot domestically.

When fascism “emerges” is when the revolutionary potential of the imperial core is at its highest

Again, also not borne out by history. You can say that fascism is deployed when there is a risk of revolution, but to say the potential is the highest is to ignore the reality that the states and periods we traditionally label as "fascist" did not exhibit any meaningful revolutionary potential.

As a way to define political moments its only useful as a way to understand revolutionary potential within the imperial core.

Maybe. This hasn't been shown though. The greatest revolutionary potential in the imperial core doesn't seem to be associated with anything like what happened in the Third Reich nor what happened to the American Indians nor what happened to Haiti. Instead, it seems to have been associated with labor organizing and with anti-war movements. Once European fascism materialized in the "Axis", revolutionary potential was gone.