[bojan]

Alex,
Let's put God aside... This is only a last resort for those impatient people who can not find (acceptable to them) solutions to problems NOW, and/or who are not willing to wait (or not willing to accept that certain puzzles can not be solved in their life time).

I want to give you here another starting point:
Assume that you have infinite plate, made of material which is perfect shield for your "pushing" particles, and a golf ball 1m above (or near) it.
Could you tell what will be residual pushing force on the golf ball?
To satisfy all conditions I mentioned in previous posts, you will have to conclude at the end (by calculations of course, not by common sense logic) that that force must be huge, infinite in fact. Because here you have ALL the universe pushing this poor golf ball in only one direction.
The acceleration that ball is suffering will be also infinite.
To achieve this, the mass of "pushing" particles hitting the ball in certain time interval (say, 1 second) must also be infinite.

From this starting point, you can imagine very easily that the mass density of "empty" space is also huge.... and so is the mass of the whole universe.
Now, according to current BB theories only 75% of required mass of the Universe must be allocated to Dark matter, the rest is known to exist and is visible.
But if we go for "pushing" theory of gravity, it is my feeling we will end up with even bigger problem. I bet it will turn out this theory predicts/requires 100.000.000.000.....etc times bigger mass of the universe. And it is not there otherwise we would already have contraction of the Universe instead of expansion?

Also, those particles (they must have mass otherwise they do not have momentum so they can not push anything) apparently do not interact with themselves at all.. otherwise the Universe would be a very crowded place. And we know it is not. Not in this sense, that is.
How can you explain those basic problems with "pushing" theory, without creating even bigger problems?

I am fully aware that I am grossly simplifying things here. I am just trying to give you counter-arguments. on the same or similar level you are using.