I'm With Stupid said:
For someone who claims to have read it, you clearly didn't read them very carefully. Dawkins is quite clear that philosophically speaking, he is one of the agnostic atheists you claim are on solid ground, and goes into quite a lot of detail about it. "Fine tuning" is just another example of the ever-retreating argument of "we don't know why this is the case, therefore God." So yes, it's quite unreasonable to believe in a god on that basis. The only good reason for believing in God is that you live somewhere where people will kill you if you don't.
Oh aye, yeah, I'm lying about having read it aren't I... It was an enormous waste of my time but now I at least know what a charlatan he is. He spent about two hundred pages setting up his sky cranes and hooks argument and then when it got to explaining fine-tuning, he had about one paragraph on a multiverse. It was laughable. His entire argument hinges on it, he's built up this entire huge argument about something which is designed needing a designer, but when it gets to the top of the argument, and the universe still needs to satisfy the fine-tuning problem whereas a creator deity needs no more sky cranes, he barely gives the a multiverse, the best scientific explanation we have for fine-tuning a paragraph. But that's his argument totally nullfied. His entire argument that no matter how complex we are, a designer would be more complex, runs out of puff and stalls next to the creator deity answer and he barely says a word... Completely pointless. As to whether Dawkins is agnostic atheist, no, he isn't. On his seven point scale he rates himself as a 6.9 i.e. nearly certain that God doesn't exist. That is a clear claim to knowledge.