Huge fluctuation over what term? Year to year? Month to month? Usually, over enough time, you get a pretty good idea of income.
You've already indicated that your fluctuations are more in the manner of manipulations. You have also previously suggested that you get a salary. If you get a salary, your salary will be what it is; any bonuses you give yourself can be evaluated over the history of your self-employment. I wouldn't expect a court to be impressed by claims of fluctuating income, when you can loan yourself a half-year's salary on a whim.

