Can you refer me to an investment where I can invest 6% of my assets and get a guaranteed 6% return on my investment while I am still holding onto and 1/2 of that investment?
Easily: buy a 6% preferred stock on margin.
Sorry that you don't see the irrelevance of that point. To make it simpler: suppose you are right, suppose banks are the only ones that get that special deal. So what? The onus is on you to show that it is contrary to the interests of American people. [ Hint: you can't have a central bank without bankers. ]
No less importantly, is another point you and many others appear to miss. Ownership and control are two different tings. This divergence is all around you, multiplied hundred of thousands of times. A laundromat organized as a corporation must have some states multiple owners. So the founder may bring on board his wife and/or daughter. But he does not want interference from those people. His lawyer would immediately advise him to create two classes of stock: one that expresses economic benefits (profits), and another control (voting rights). So the wife is part owner but has no say whatsoever in the running of the business. This is commonplace.
Fed is run in a somewhat similar fashion: the member banks own the Fed but even taken together, constitute only a minority when it comes to decision-making. Even if you could manage to organize a conspiracy of hudreds of banks, they would be still outvoted by appointees to the Board of Governors.
So, the conspiracy theories make factual mistakes in their claims of Fed ownership, but an even greater mistake when they focus on ownership in the first place. Many people believe, mistakenly, that ownership and control is the same thing. It is not. And there is nothing mysterious about that: ask your neighbor who owns laundromats nearby.