Considering the definitions you have written down (and not the actual definitions of these words), I'ld say that both theism and atheism are equally illogical, since they both establish beliefs that can't be supported with evidence.
I think this is quite incorrect. Theism could easily be supported by the deity simply providing that unequivocal evidence, which all theists suppose it is totally able to do.
The same is not true of atheism, since atheism does not make a claim at all, but rather simply states, "having seen no such evidence, and not expecting to see any, I do not believe in the existence of a deity that is in any way active or involved in the world." Yet, that is still not enough to make the claim that "of a certainty, no deity exists," because there is always the possibility that the evidence that would prove it could be deliberately hidden by said deity.
Agnosticism, on the other hand, has all the "evidence" as theism or atheism, but feels, for whatever reason, unable to make a decision. This seems to me to be a bit bizarre, since, as I said, any real evidence for the existence of a deity involved or active in the world would instantly decide the question. So the agnostic must admit that no such evidence exists, or he could no longer possibly be agnostic. Therefore, it would seem that he ought to reason, from that, the atheism is more likely to be correct.