After wading through 100+ irrelevant posts about religion, Mohammad, Hitler, homosexuality and God knows what else, there were maybe a dozen posts that actually addressed the original question.
As I understand it, the original post asked two questions:
1- Did Darwin believe that certain races are biologically inferior to others?
2- Is evolution proven?
The first question is easily answered. If the quoted text is accurate, then Darwin clearly believed that certain races had evolved further than others. But, so what? His personal beliefs are irrelevant and do not invalidate his science.
I will break the second question into two parts:
1a- Is the process of evolution proven?
1b- Is the mechanism of evolution proven?
In response, I would say the fossil evidence provides a lot of evidence in support of 1a. We even have experiments and observations supporting 1a. But there are open questions about 1b. Specifically, the OP mentioned the probabilistic challenge to evolution. I assume he was referring to the work of John Sanford and other scientists who argue that, given that the fundamental mechanism of evolution is chance mutation and, in a binary code made up of hundreds of billions of digits, the chances for a beneficial mutation are extremely small, almost all chance mutations will have a negative effect.
Personally, I believe in evolution, but I agree that this challenge hasn't been sufficiently explained by neo-Darwinists.