The answer to your question is NO. You cannot reset your battle points for the same Steam account.
The other part of your question, about being not a good player, is a very common thing which all DOTA beginners experience. I myself have went through this kind of feeling so don't worry, this happens with most players. Remember DOTA has a huge learning curve and 300 hours of gameplay experience is not much if you really want to master the game. I have been playing DotA for more than 3 years on and off and I'm still not 'Dendi'. On my best day, I am an above average player.
Let me ask you one thing. Why do you think some players are pros and others are noob? What is the difference between them? I know so many players who are my friends, who mastered the game in less than 6 months and I also know other friends (whose count is way more than the good ones) who play like crap even after playing regularly for more than 3 years. The individual's skill level comes into play here. Also, doesn't matter how good you are, there will always be someone better than you. So don't get disheartened.
As far as I think, DOTA is about 'presence of mind' more than anything. Your mind is your greatest asset in DOTA. Its all about mind games, though various other factors such as reflexes, map awareness and overall knowledge and experience of the game also counts.
So if there is a player better than you, you should understand and accept it in a positive spirit that he is more skilled than you at this current point of time. See, I am not demotivating you or anyone. But if you want to be better than him, you will have to work hard, practice more (AND MORE) and LEARN as much as you can from other experienced players. The best way to do that is by watching DOTA replays of the teams which you like (good teams like NaVi, E-Home etc.) and of players (good players like Dendi, Puppy etc.) playing heroes which you like. You can find these replays on the internet freely. Try doing that and you will definitely see yourself improving.