I wonder how they know how long I am in France? They should also first have something that brings me under their attention. They cannot check every person walking around in France. There are no borders and no control as long as you don't take a plane or an international train. And how can they find out how much money I make, and where I make it? I can proof that I have enough money in my savings accounts for the rest of my life.
I never stay 183 days a year in any country. So the only country that can tax me is Bulgaria.
If I am right the 183 days rule is only valid for people who are employed; self employed people don't have to care about this rule. Not 100% sure but fairly sure.
From where I'm from in the EU this is not the case. All income is taxed, salaries and capital gains the same way and the residency rules are the same. Typically as self-employed you're still considered an employee, they're just interested on how much you make and that they get their share.