"Equality before the law ignores the important pre-existing inequalities in power between people, and it is as such far more useful as a tool of bourgeois supremacy than as a social leveler."
You forget that is was well known by the framers who took measures that it should not become such a tool. This was the evil of pure democracy, in modern days described as two wolves and a sheep voting what to have for lunch.
So they didn't create a democratic government. They created a republic. Further, they created a constitutional republic. Even further, they separated the powers of this republic across three independent and equal branches of that government.
They also realized something apparently neither you nor Marx are aware. If you bias any functioning of the government toward one side over another, no matter what manner of fairness and equity you mean to implement, this bias will shortly become the very tool you and Marx supposedly oppose.
Freedoms are never taken away by whimsy. They are always taken away for the very best of reasons.
But no matter how good those reasons are at the beginning of the process, the end result is the same: the loss of freedom--tyranny.
That is why it is often said that you can have equality (freedom) or you can have equity, but you cannot have both.
You also point out that the men who advanced the concept of the right to private property were themselves, by and large, wealthy land owners. But you fail to show how these proletarian land owners increased their wealth through through the government they successfully created. In fact, the early history of the US is full of land give-aways to common men. Millions of acres of unclaimed land given away to anyone willing to live and work on it.
This made a significant number of Americans members of the propertied class. This is strange behavior of people who want only to "bend the laws to their favor."