It's a pretty big claim that ethics has "no reason but your belief in it". There are plenty of logical reasons why one would want to behave ethically, even self interest, beyond you simply believing it.
There are also some moral principles that follow directly from factual matters, provided some very basic first assumptions are made. Theories of just resource distribution and social justice are of that kind. The principles that get things going are very basic, e.g. reciprocity, generality of moral statements, and fairness in the sense of trade/bargaining/exchange fairness get you very far.
It is a myth that religion provides values, as it can be shown very easily by historical comparison that it never has. The values defended by major religions such as Christianity and Islam have changed over the centuries again and again. Modern Christian values, for instance, mostly come from the enlightenment movement and were not endorsed at all earlier. (Christianity is just an example, AFAIK this is true for all religions.)
Churches and 'holy men' have always had a vested interest in selling their values as a product of their religion, though, and they are very good at selling this false story to the public.
Also, for the final paragraph: Your theory of religion seems to be based on intelligent design. I think it is more accurate (and less prone to conspiracy theories) to think of the evolution of religious memes in darwinist terms of "natural" selection.