Previous arrest is not evidence though. You can't just arrest somebody for something you have zero evidence for just because they were previously arrested for doing that thing. He has every right to resist. Plus, if you watch the video, Garner's "resistance" basically amounts to him waving his arms around before the guy grabs him from behind and puts him on the ground. Obviously this technically led to his death because it has a link in the chain of events that ended with him dying...but you could say the same thing about him leaving his house in the morning getting out of bed. The point is that he was in no way at fault for his death.
Well, that's an interesting proposition. You can resist arrest as long as you think you're innocent? That would be a strange world. In reality, if a police officer sees you break the law, they can arrest you. They can arrest you for putting your feet up on the subway or riding a bicycle without a bell. As I understand it, they saw him commit the crime so it was 100% a legal arrest. But, I agree with you that the fault here lies with the NYPD. The boys didn't need to get all Ultimate Fighting Championship on that guy.