Where to start, I'm tempted to say something like "grow up" and leave it there but that doesn't really explain anything.
You have to realise that you are reading a story, you see things the other characters don't for example though we see that Harry is going to fight Voldemort in the first book no actual character would suspect the two having to kill each other until they hear the prophecy and Dumbledore in particular did not believe it.
1. Dumbledore never planned to rule the muggles and though Grindelwald certainly become more and more evil from questionable morals to start with he was not Hitler. There is no mention of death camps only political imprisonment which is typical of any dictator and Grindelwald certainly was a dictator. I'm not defending him I'm just saying the Hitler comparison adds nothing to your argument, argue about what Grindelwald himself you can't just say Hitler and assume that makes an argument.
2. Grindelwald is a Swiss name, google it.
3. He did the only thing he could when Riddle was a kid, you want him to deny a child any education because of one incident of which the details are unclear. You can't do that in the real world, you are confusing the perspective you have as the reader knowing that he will become a killer later in life. If we follow your advice no one from a broken home is allowed to go to school.
4. Just because they don't go into detail about what the order of the phoenix did in the first war doesn't mean they did nothing. Going back to your Hitler analogy there were a number of organisations in WW2 smuggling Jews away from the Germans. They didn't stop Hitler and you may not know the details of their operations that doesn't mean they did nothing, they saved lives.
When we get to the start of the story Albus has made only 1 real mistake: not recognising the problems with Grindelwald when they were friends. Again if you are in the real world you have no right to demand he go and kill Grindelwald. Going back to Hitler again you can't blame every sniper who was alive at the time for not immediately heading to Germany and shooting Hitler. The fact that Dumbledore did go and defeat him counts in his favour.
5. Slytherin house is required for literary purposes but we know for example that Lucius Malfoy is on the board of governors and that the ministry has a strong undercurrent of bigorty, it would have been impossible for Dumbledore to do anything about it.
6. The last battle in the last book is joined by a number of other races, trying to get support from other races is what the order was trying to do. I don't see how you can blame Dumbledore for Sirius' death, he was chased from the school, turned up at the ministry and saved everyone.
7. He recognises the mistake he made keeping Harry at the Dursleys they treated him bladly but not as badly as many fanfics have him being treated. You don't mention this but I thought I should. It's the one thing I really disliked about Dumbledore, he suspects early on that Harry must die and says he is going out of his way to give Harry as much of a life as he can but he leaves him with the Durdleys. I understand that there are literary reasons for this though.
Dumbledore is not evil and cannot be blamed for everything you have tried to pin on him. He is a flawed character but he is a good character.