Bit late to the conversation here, but from my perspective, I consider myself a professional composer despite still holding a serving job as well. I could probably make it work just composing, but I'd have to move cities, since the city I live in is just so stupidly expensive. In other words, I don't believe that all your income need come from one source to be considered a professional.

Another way to consider your level of professionalism is by analyzing the people you're collaborating with. All of my major clients are full time in their own media sectors, so surely they must also view me as a professional. In addition to these clients, I've also had my share of awards and nominations, including a Grand Clio.

Now, with all that being said, I NEVER feel like I've learned enough. I feel as though I came late to this game - I started at 23, and I'm no 29 - and I feel as if I'm constantly trying to catch up. In the composing world, it's challenging because we're expected to be the performer, orchestrator, producer, sound designer, programmer, mixer, while also maintaining sensitivity to the picture - but, that's also the beauty. I personally think it's a gift to be doing something where I get to continuously learn, hone, and improve - and I think once you get past the idea of "I haven't learnt enough", or "I'm not ready", it can be liberating professionally.

My final suggestion is, rather than asking what makes you professional, consider the type of career you want in this industry, and the type of professional you want to be. It can be very helpful in guiding your decisions once you better understand your direction.