How could an equal balance of power between the two parties in Congress be achieved?

The only way to have a truly equal balance of power would be to have the same number of democrats as republicans. One party could not be in the majority. While this could be achieved in the Senate, where there are 100 members, it would be hard in the House of Representatives, where there are 435 members (number can't be equally split in half). Each member would have to have the same amount of control and influence as well. Without an equal representation of both parties, the power can never truly be balanced.