I really don´t care about this - I just hope you got the comparison point here:
You don't care about precision? Then you admit you aren't doing science?
You wrote:
First, qouote: "A vacuum is space devoid of matter" - which is a restricted and even contradictive defintion, as there´s no such thing as *an empty space*. Otherwise you would have to discard and binn the very idea of a CMBR too.
Secondly: When speaking of a *vacuum density* in general, you have:
1) An unexlainable and untestable Big Bang
2) A still increasing expansion velosity.
3) A *gravity assumption* which logically contradicts such a general and increasing velocity expansion.
Arguments on *forth and back* and in all contradictive directions at the same time, is what you really have.
If having 1 molecule of hydrogen in every meter sounds like space is full of matter to you, then there is nothing to argue. The space between those molecules is empty of matter. And that is certainly FAR less matter than what you get in near Earth orbit (where the drag is).
The CMBR is not made of matter, but of photons.
The BB theory *has* been tested in multiple ways. And, no, the assumption of gravity does NOT contradict what we have observed. But you do have to understand what the theory predicts and not simply deal with vague generalities.