It looks as though about half of your objections have to do with SIAI and the other half have to do with charitable donation in general. In my opinion, there are very strong arguments for donating to charity even if the best available charity is much less effective than SI claims to be. If you find these arguments persuasive, you could separate your charitable giving into 2 phases: during the 1st phase, you would establish some sort of foundation and begin gradually redirecting your income/assets to it. During the 2nd phase, you could attempt to figure out what the optimal charity was and donate to it.

I've found that this breaking up of a difficult task into phases helps me a lot. For example, I try to separate the brainstorming of rules for myself to follow and their actual implementation into separate phases.