Three points:
First. The quote about 1000 people going free pertains to trial, not police interacting with criminals in the street. A wrongful conviction doesn't result in an LEO dying, whereas hesitation in the street could.
Second. You're assuming that the 1,100 killed were killed unjustifiably. I don't believe that is remotely the case. We hear about Tamir Rice, Eric Garner, etc., but those are the extreme outliers. That's why we hear about them. The media focus on them creates a false impression that the police unjustifiably kill people every day. That just isn't the case.
Third. Is one too many? Yes, it is. But we have a human system that will never be error free in this regard unless we de-arm the police. I don't know the number of police killings that are unjustified, but I would hazard a guess it is well below 10%. Even assuming 10% is the right number we are talking about 110 unjustifiable deaths per year in a country of 330 million people. That number isn't perfect, but I think it is getting pretty close to as low as we could ever get in a human enterprise under the constraints we are dealing with.