This is where I take issue. Even using the term intelligent design ruins any form of reasonable discussion. Everything anybody responds with can simply be dismissed by the intelligent design statement. "How did the big bang happen?" ... "God made it" etc. etc. Doesn't really help anything. That is the equivalent of giving up on trying to understand or rationalize anything. This is the very reason intelligent design is not taught. There is nothing to teach. It is just a cop out.
Yes, all scientific 'facts' are merely well evidenced theories as well, but going this way in the argument just descends in to 'what is a fact?' There are no ultimate facts. Even what you can see, hear, touch, and taste is not a fact. It is just a generally accepted principle by all the cells in your brain that what you are seeing, hearing, touching or tasting is there. I accept religion as a faith or a belief, not as a theory. Religion cannot be proven, therefore cannot be a theory. Hence my problem with the main religious teachings/worship (see above).
On the question of "where did we come from?" Well, the latest data scientists are getting is increasingly backing the theory that the big bang is a cyclical event (universe expands/contracts to nothing and then all over again ...). Life on this planet may well be just a tiny chance of things meeting at exactly the right moment in the nth interation of this cycle. Just like a computer making 1 error in its billionth process. Which makes us awesomely special. Also, in a couple of years they will be able to re-run the Hadron Collider at higher energy levels, where they have narrowed the Higgs-Boson down to, and should be able to find it (they are very close!). This really will provide good evidence for the big bang theory etc.
The universe. Well I subscribe to string theory, and thus alternate universes. Gravity seems illogically weak as a force (lots of complicated science blah blah), and the rationale that it slips between the different universes set together like pages on a book seems a nice theory. Again, evidence and theories of alternate universes are increasingly coming together. But again, these are just theories.
Life outside. Well, that is complicated. Suffice to say, it would be an awful waste if we are the only ones.