stuck in 600s-800s
Oh, and by the way, the standard for success is NOT never blundering again. Even grandmasters blunder. In some sense, whether or not you blunder is completely unimportant... what's important is whether or not you're blundering in the same ways over and over. If you can identify a type of mistake, and change the way you play to diminish or remove that mistake, then you're going to improve, guaranteed.
This is good advice. I also will take these suggestions.