These questions are being asked as if materialism is true. I hope my answers indicate how differently idealists think about things in general. Also, in your third question you are ignoring what I have said two or three times now about the nature of scientific evidence and the limits of science.
1. If consciousness is all around us, and we live in it rather than it inhabits us as my notion, why cant mechanical systems obtain consciousness if we dont know the mechanisms of how we obtain it?
Short answer: We don't obtain consciousness. Rather, consciousness creates a body, to experience physical reality.
Longer answer: A machine operates according to strict spatiotemporal rules. How, then, could it be aware of time passing? It goes from one state to the next. To be aware of change (which is another way of saying "aware of time passing") it must somehow unify a sequence of states into one "gestalt" (that is, "an organized whole that is perceived as more than the sum of its parts"). A common mistake people make is to think of "now" as a point in time. Actually, it lasts several tenths of a second. (Try it: watch a bird flying past, and -- if you think consciousness is nothing but brain states -- note that to know that the bird is moving you have somehow unified several thousand sequential brain states into one "gestalt". How could the brain do that? To appeal to some meta-state is to get yourself into an infinite regress.) In other words, to be aware of time passing we must in some sense be operating outside of time. How do we design a machine to be outside of time? One possible answer would be to appeal to some sort of quantum machine. But this amounts to saying that quantum reality is fundamentally non-spatiotemporal which, if one thinks it through, means so is everything. Which, by the way, is what mystics have been saying for millennia. Perhaps we should pay attention to them.
2. If it takes an organic brain to achieve consciousness, at what level does it obtain it? simple life forms, complex, vertebrates? What about trees and plants?
If consciousness is fundamental, then it doesn't make sense to ask "when does a body obtain it". Consciousness creates bodies, from plants to human bodies, as well as the mineral background in which to operate. (Note: they are not just created and then exist on their own. Rather, consciousness (human and non-human) is constantly sustaining them in existence. Another big topic.)
3. There should be physical manifestations of consciousness if it is as you describe. Measurable with experiment. Otherwise how does it manifest itself? Other than saying it is so, how can we prove it? This is where it gets religious in nature to me. It is because it says it is.
Everything we sense is a physical manifestation of consciousness. Indeed, that's what the senses are: the manifesting of physical reality.
It is no more "it is because it says it is" (or provable) than is materialism. It is a hypothesis. It is a better hypothesis than materialism, because it can explain all of our experience, while materialism doesn't even have an explanation for experience itself.