I presume, you have the residence permit after §30.1.3g Residence Act (AufenthG), exactly §30.1.3g - for the spouses of foreigners who have Blue Card EU.
The rules for the case of separation don't normally differ from other spouse residence permits. You must be married and live together for 3 years in Germany before separation, only then you have the right to obtain an independent residence permit and prolong it (§31.1.1 Residence Act). If you separate earlier, it is only possible to get this independent residence permit in so called hard cases (for example if violence is concerned or your interests are especially in danger). It is normally also a condition to obtain it that you earn your living fully and don't need any help from the state. But only this condition without a hard case can be not enough.
The Ausländerbehörde can possibly claim that you return to your country and ask for a job visum, because you can't easily change the aim of your residence inside Germany. You can check if you have a chance to obtain a visum for a special job you do now because you need an agreement of the Bundesarbeitsagentur. Sometimes it is the easiest option, but you better ask Ausländerbehörde to give you a so called "Vorabzustimmung" (preliminary confirmation that if you apply for a job visum in an embassy, the Ausländerbehörde will have nothing against it). With such a document it can be much quicker to get a visum.
If you want to stay without leaving Germany, you will perhaps need a lawyer. Anyway try to find a good councelling center or a good lawyer for migration questions in your area.