Maybe not corporations, but the wealthy were definitely kicking up a storm over British taxes and import restrictions, and then later driving a lot of the pro-slavery arguments.

I think private banks were...

No, but powerful slaveholding interests were a major factor in the design of our government. It's the reasons our voting system favors low-population states--because slaves only counted as 3/5 of a person and the slaveholders were worried this would mean less representation in government and the danger that owning slaves would be outlawed.

The 3/5ths compromise was about giving less representation to slaveholder states, and was not a moral judgment on the value of slaves.

Slaveholder states would have been perfectly happy for representation to be 1:1 for slaves vs. non-slaves.

Right, they had less representation so they needed to make up for the loss of power with the Electoral College system.

Right, the Electoral College and the Senate benefitted slaveholders by granting them more political power, not the 3/5ths compromise.