Hi! I understand work situations can be hard sometimes, so I'll try to give you the other side of the coin: I am that guy.
I'm doing great at my current company, but I had a lot of issues similar to the ones you described on my previous one, but I was the "rockstar". I'm going to give you my honest view of the facts. It can be biased, of course, but my in my mind, I always had a reason for my actions. You'll decide whether it was justified or not. Now, diving into your examples:
we got an email that a website he wrote was broken, so he forwarded it to us. A coworker of mine spent 2 hours trying to figure out what the issue was, and it was because of a bug on a function this guy wrote. He could have solved it in 15 mins likely. When my coworker pointed out that in the end it was his fault, he looked annoyed and ignored him.
Honestly? Pointing fingers is terrible for morale. I would have expected the guy who got assigned the task to do it without complaining, the way I would have done it had I been in his shoes. Besides, the whole "he could have done it faster" is also moot. With that criteria, people wouldn't grow in a company as they would always be stuck on the same projects, right?
our boss asked him to estimate a job, which he did. The job was then assigned to another guy but the estimate was kept, and this guy is going crazy trying to complete the assignment, saying that the first estimate (10 days) was clearly wrong.
Did your boss tell the other coworker to consult with him for development? Why didn't management ask the actual developer to do the estimate? My guess is he didn't. I used to get tasks like these. A few of my old coworkers where knowledgeable of the tech they had to do their jobs in, so management asked me and then passed them the ball. Was this ok? I'm not sure. But management sure as hell didn't play it right, and I'm guessing your case is similar.
I was asked to estimate something two weeks ago, and I said 2 days. For some reason, the same person also asked him later on, and he said "I looked at the code and this task takes 1 day", and they went with 1 day. WTF? Maybe I need more time, maybe I need someone to explain it to me, or maybe I still need to look at the code, etc. If the point is to show it can be done fast, then why doesn't he do it in 15 mins at this point???
Same as the previous point. In addition, you have no idea how it was written and you still invented a number? The way you describe it, he took the time to analyze the work, you didn't.
When you ask him for help, most of the times his answers are "google it", or "I can't help you, you need to do it yourself", or "I can't do your job for you, sorry".
Well, this can be annoying. I used to get a lot of these too. What I did was filter out those who put some effort first from those who didn't. The ones who came to me first were immediately shut down because I'm nobody stack overflow, and I wasn't getting other people's salaries. The ones who put some effort first could ask me anything and would get help from me every single time. Sure, those I turned down probably thought I was an ass.
6 months ago we had some issues finishing customizing a wordpress website, so he stepped in and we shifted to other things. The job got done and the client was happy. Last week a coworker of ours was asked to make some changes to the same website, and holly shit, he spent hours trying to navigate what this guy had done to make it work 6 months prior.
So you couldn't do the job, he had to do it for you, and now you complain he didn't do a good job? I'm not even commenting on this...
Finally, a client complained recently that the product was extremely slow. The product was written by him 2 years ago and then he moved on to other things. A coworker and I (we were now both in charge of the project) were trying to figure out the reason and eventually asked him for help. He found out that the problem was a function he had written years ago, and when he realized this, he said "well, guys, this was written 2 years ago, I haven't worked on the project for a year, you should have maintained the codebase" Unbelievable...
He's right. He's not on the project, he's not to be blamed, end of story. What is this, a witch-hunt to offload blame? I had this thing happened to me twice. The first one was similar to your situation, but it wasn't a performance issue, there was a broken functionality. I had explicitly written down that there was no time to finish it when I passed it on, and the team never did. Months later they tried to say it was my fault to cover their asses, and I shut them down quick.
On another occasion, the finger-pointing attitude was brought abruptly to an end when I realized the client had been sending emails for weeks about the issue and the team decided to ignore it because "debugging that code was a pain in the ass". Therefore, when the guy sending emails blew off, they tried to say it was my fault because the code they didn't want to debug was mine. I brought the coworker in front of our manager after that and explicitly "burned" him for this.
I don't want to be a dick about these problems, but my point is, there are always two sides to the story. In my case, half my coworkers didn't like their jobs and were bad at it, and tried to scapegoat others all the time when things went wrong, not just me. However, I built myself a reputation of not to be messed with otherwise it would have been hell working there. I'm sure they thought it was hell working with me also, but what can I tell you, life isn't easy.