Is it possible to write invoices without having registered as a business in Sweden? If it's the case, than just explain it in a cover letter. Attach recent invoices and highlight the corresponding transactions on your bank statement.
I've had a similar experience with Ankara. Applied mid December, got a request for additional documents in January, after which nothing happened for a looooooong time. They did not answer my e-mails either. And I got approved a couple of days ago, after my intended departure date.
I understand your frustration, but look, it's the way it is, and it was no secret. Escalating whatever you think is unfair won't change anything. Why don't you just travel to Việt Nam or Cambodia, stay there a couple of weeks and apply from there?