D,
I suppose to an ignorant person hundreds of years ago a person asserting that the earth was a sphere would sound like he was just making an assumption, and yet there were those who could confidently back and provide evidence for such a claim. Back then it would have sounded dogmatic to say the earth was a sphere. Well, then I suppose it's okay to be dogmatic sometimes when you are right and you have the evidence on your side. It's just as dogmatic to assert the earth is a sphere today, and yet we have no qualms about it.
What are assumptions to you is merely lack of knowledge on your part. If you would educate yourself on the theories you are talking about, you would see the evidence and the reasoning behind the "assumptions" as you call them. You will find, with education, that scientists rarely do ever dogmatically assert what is uncertain. Yet they are not afraid to talk confidently about theories which have been tested over and over again to the point that they are common knowledge.
Remember that if there is one thing that the scientific method has taught us, it's that our intuition is usually wrong when it comes to areas in which we have little exposure. So just because something might sound crazy to you, doesn't mean that it's automatically wrong. It just means that your brain is not used to thinking about how things really are because you are used to thinking "intuitively".
I agree that the questions you are asking are extremely basic and can be answered by you doing a little bit of homework. It's not fair to expect people on this board to spoon-feed you the information. We've pointed out an area where you are ignorant of the latest scientific findings, now it's up to you to fill that knowledge gap. That's what we had to do! You have no business finding "flaws" in scientific theories that you know nothing about. How would you like me to tell you that you run your business wrong when I don't know the first thing about what you do? It's ludicrous.
rem
P.S. Some books that helped me are:
Five Ages of the Universe, Fred Adams and Greg Laughlin
Six Easy Pieces and Six Not So Easy Pieces, Richard Feynman
'A scientific opinion is one which there is some reason to believe is true; an unscientific opinion is one which is held for some reason other than its probable truth.' - Bertrand Russell