How can I limit the tax liabilities of my online business?

You need to retain a tax lawyer and provide the lawyer with the current facts of the business along with your future plans for the business. This is not a consultation to be performed over the internet. The answer depends, in part, on the state in which your business is established and the states from which it is deriving revenue and how it derives revenue from those states. Read about the current antagonism between Amazon and states like California and Illinois and you will get a flavor for the issues.