Good to hear you are making progress
I'm finally recognizing the problems that give me troubles with the game.
It appears you have created an alibi. You don’t make mistakes. This belief causes you not to get better because you think you are already good because “you don’t make mistakes”. In order to get better you got to ditch this delusion that in some games you don’t make any mistakes. Again I challenge you to post some of these games to prove you are telling the truth.
From the looks of it you are a normal sub 1000 that plays blunderfests. I will add that you make normal mistakes that are common to all beginners. You just simply play the first move that comes to mind without considering other checks captures threats, etc. All you need to do to get better is practice the skill of making candidate moves and thinking about multiple candidate moves before you make a move. After you get good at this you will start to develop intuition and won’t need to calculate as much.
Let me just add I have recently been having a high win rate percentage, and then I got into a sort of slump. I know I made blunders in all of those games. I just wasn’t playing good. I am higher rated than you and even I can’t post a game that shows I made no blunders. I could say those people were cheating, but rather I am taking those losses as a learning opportunity. I am going to study my mistakes, and drill the correct moves, so I don’t make those same mistakes again. If people would just do that, then maybe the forums wouldn’t have so many posts like this, “ hi, I’m Joe. I suck. How do I improve?” That is basically the substance of a beginner post of someone wanting to improve here.
Ditch the alibi
1. I tend to play too passively.
This is something I've been trying to deal with; I've been trying to do better at seeing attacking opportunities and jumping on them, though it's a bit of an uphill battle.
2. I often assume I'm losing when I'm in fact winning, or at least have the advantage.
This is a problem I've had for a long time, but I've only noticed it recently. In some games I won that appeared pretty close, or even losing until my opponent messed up, I'll look at the review and find that I was apparently doing quite well. I'll be sitting there wondering where I made a blunder that turned the game against me, but it will turn out that I didn't even play a mistake; just a handful of inaccuracies at worst. It's a weird feeling.
3. I have the endgame skills of a fried toaster.
Pretty self-explanatory. My games rarely progress to the endgame, so I don't get a lot of time to not suck at them.
The first step to getting good at something is understanding why you're not good. I'm making big progress already.