Exactly how was the South paying 50%-80% of the Federal budget? Income Taxes, property taxes,
Since I believe it was BroJoeK that came up with the 50% number, and since he is on your side, I will let him explain it to you.
This would be one of those "admissions against interest" and therefore you know it is likely to be the truth.
But I notice you are now focusing on how this is possible, rather than objecting to the idea of the Federal government being primarily funded by slavery.
At some point, if you are being honest, you will have to acknowledge that the Federal Government was funded to some level by slavery. You will also have to note that the Federal government was not so morally pure that it would reject money directly traceable to the labor of slaves. Indeed, it wholeheartedly embraced that money.
The primary objection by the Federal government was to it's loss of money and power; That such lucrative assets were no longer under it's control. Again, they could have stopped slavery in Maryland a lot quicker. They already had plenty of troops there.