No, they don't know.

SEO is 100% pure speculation, as there is no way to validate why Google ranks things the way they do. The only people who do know for sure are closely monitored Google employees who value their bonuses.

No, if anything it will affect your site negtivly because it will make your site slightly slower. I suggest ignoring the tinfoil hat SEO community and follow the official Google guidelines.

I can't think of many sites these days (that aren't personal blogs) that don't have some kind of analytics built into it.