I don't think or believe there is anything called a professional gambler, in fact let me break it down a bit. When talk about professional we are referring to someone who can control themselves while gambling and also knowing when to stop, when to start and how much they should used to gamble or not to gambling. When all these are being put in places we can say that such person is a responsible gambler, because they weren't allowing gambling to over-will them neither are they gambling for money making even though our attention is being focused on that but at least they are also bearing the risk by using what they can afford to lose while gambling.
All the qualities you mentioned are already part of what a professional gambler has. They call themselves that because they’re in it to make money, not just for entertainment. But let’s not assume that being a “professional” means they’re raking in tons of cash. Some are profitable, some aren’t, the only difference is they take gambling seriously. Still, no matter how skilled or experienced, the outcome is never guaranteed.