Question About the Universe

Catholic Scientist's analogy is useful here:
EvC Forum: Size of the universe
(In fact it's not even a full analogy, it's just making the properties of a four dimensional space/shape, the universe, more obvious by using a two-dimensional space/shape that shares some of those properties)So the Big Bang is the North pole and every point in time after that is a circle of constant latitude. A circle of latitude being all of space at one time. As you the circles get larger the further south you go, so the spatial dimensions of the universe increase the further along in time you go.Since the circles represent the whole universe at a given time, a point in space at a given time is like a point on a given circle.So phrase your question in terms of this analogy:
The centre of the universe from which everything is accelerating, would be the equivalent of some special point on one of the latitude circles. However there is no special point on these circles that the circles are expanding way from, they are expanding "away" from the North Pole
Simply as a consequence of being circles on a sphere.Similarly the universe is not expanding away from some point where the Big Bang happened. It's just that space is getting larger as you move forward in time (down the sphere).Again, if you reverse time the circle shrinks and all points on the circle converge on the North Pole, so the North Pole "happens" at all points on the circle. Similarly the Big Bang happened everywhere.

A simple example might help.Take a universe with only ten points, labelled by the integers from 1 to 10. This universe also has only two objects, labelled A and B. A sits at location 2 and B sits at location 8. The distance between A and B is obviously six points.Distance traveled, for objects in this universe, is just the number of points they've past through. How far apart the points are in whatever fictional background you choose to visualize them in, is irrelevant as that background has no physical reality in this model.Now simply add ten more points into the universe, the half-integers let's say (i.e. 0.5, 1.5, e.t.c.). There are now twelve points between A and B, so they are further apart, but they haven't moved, they're still located at points 2 and 8.It's simply that more space has been created between them. It's the same with our universe.

In truth there is no force. New space is simply being created. Every second, for each cubic meter, about 10 cubic attometers are created and hence there is suddenly more distance/space between each object.So just looking a one direction, rather than a volume, for every meter about two attometers are created.The distance between here and the Andromeda galaxy is about 2.54 Mega light years, add two new attometers for every meter along that distance and you get an increase of about 2 centimeters per second (actually 1.8 centimeters).Now, even though the reality is that 2 centimeters are being created, you can think of it like the Andromeda Galaxy moving away at a rate of 0.02 m/s. That's nowhere near enough to overcome the fact that it is approaching the Milky Way at ~120 km/s.

It certainly is. Although at least with General Relativity you can at least "understand" what it is that you can't picture. In quantum mechanics you don't even have that!

Yes, essentially. Space doesn't have an energy density or mass properties.

For certain spacetimes you can tell how much mass is needed to create them based on the properties of the spacetime. This is sometimes referred to as the mass of the spacetime. Of course the spacetime does not actually have mass, you can just infer how much mass was involved in shaping it.

No, not at all. Spacetime has a shape, that is what the curvature of spacetime refers to, but it's not a form of mass/energy.