No, all scientific studies correlating extended screentime with any visual impairment are yet to establish a causal link. It is premature to arrive at the conclusion that screen time leads to myopia.
Yes, if you are asking this question, it means that you have recognized a problem in your lifestyle. Playing video games is not evil by itself. Having it control your life to the point that you are questioning yourself is a sign of waning self-discipline. Some other hobbies and activities are far better instead of playing video games.
No, there is no conclusive scientific finding that video game addiction is a medical condition. Addiction to playing video games might be a sign of other mental illnesses or, simply, people might just have an intense passion for this hobby without suffering from any sickness. Not everything should be attributed to disease even if it is as obsessive as hyper-consumerism.