I am an ex-felon at the Federal level. What is the maximum amount of grant money available to me for starting a business?

There is no such grant that I know of. Call or visit your public library and talk with a reference librarian to find out about local helps for possibly money and more likely practical advice. Local churches, Catholic Charities and Lutheran Social Services, SCORE, your township, etc. may be able to help in various ways, especially if you have a good idea/plan in mind.

Popular myth....

There is no grant money given to you simply because you're a felon. If that was the case, people would be doing it left and right just to get grant money to start a business.

Exactly... why should felons get free money the rest of us can't get. We would be committing crimes too to get that handout.

You do what everyone else does, borrow money off friends and family, borrow the rest (anywhere but a loan shark), and hope the business doesn't go under before you get your investment back.

The myth persists because there are so many scam sites claiming 'free money for felons.' I used to see ads for them right here on AMHD, whenever anyone asked a question about being a felon.
PS: You are not an ex felon. A felon remains a felon.
The ONLY possible grants are education ones. You might want to look into that, such as a one year program to learn a skill. Try the Education Connection. But no funds go to the student.