@1
600 is not impressive at all.
Always check your intended move is no blunder before you play it.
Hang no pieces, hang no pawns. That little mental discipline is enough to reach 1500.
You might be right that 600 is not impressive (I am currently in the 700-800 range, and am aware I am not very impressive either). Your "advice", however, is overly simplistic and unrealistic.
Yes and no. "Don't blunder" is easier said than done, but it's also basically the core of winning chess at sub-expert level. Most games at that level aren't won through accurate play, they're lost through blunders. Often, a player will spot the blunder as soon as they play it, but by then it's too late. Learning to recognise them before you play them is key, and no amount of opening prep will help stop you blundering in the middlegame.
Tactics training can help, but the tricky thing is to see your opponent's potential tactics as well as your own.
There are blunders and blunders, of course. Some of the blunders the engine picks up are because they expose you to a devastating combination from your opponent, but your opponent still needs to spot that combo. At a 600-level, it's probably more likely than not that they'll miss it. But stuff like hanging your pieces, walking your queen into knight forks, etc. - that's the kind of thing that loses games and can be minimised with a bit of training.
Ratings are very subjective, and it really depends on your experience... if you've been playing regularly for a year, 600 isn't very good... on the other hand, if you've only been playing chess occasionally for a couple months I'd say it's pretty normal. As for winning/losing streaks, it's also very dependent on your mental state. Sometimes, when I'm wide awake and "in the zone", I've been able to get completely winning positions over GMs over the board. When I'm drunk/tired, I'll completely forget my queen is hanging.
Just remember, no matter how good you are, there are almost certainly tons of players who are much better and tons of players much worse than you.