There seems to be a problem with distant galaxies not decelerating as fast as expected by Newtons rules.
Imagine our galaxy pulling on a distant galaxy and causing it to slow its speed away from us because G pulls it back.
If the universe is closed then gravity can travel to this far universe around the back and pull from the other direction.
If it is so far as to be on exactly the other side of the universe then G from our galaxy will cancel to zero.
Further away and it will be seen to be accelerating away from us.
For these galaxies ,look behind yourself,there it is coming toward you (or at least not going away so fast).

Of course Newton's formula does not hold at cosmic distances in curved space. It is valid only in a thought experiment built on Cartesian coordinates and Euclidean geometry. It is a close approach to what we observe over relatively short distances, meaning galaxy-sized or smaller, and as such is in excellent agreement with any measurements Newton was able to make, along with everything done for about two more centuries.

If I am not mistaken, your mental picture of a closed universe is not an accurate rendering of the current theory, but I will have to yield to those more knowledgeable than myself to elaborate.

If gravity "moves" at the speed of light, then it doesn't go fast enough to have "wrapped around".

The expansion of space is (in effect) faster than allows light-speed travel around.

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Well, I'm a simple kind of guy, so here's a simplistic example. Imagine a universe with nothing in it but a hand grenade, which then explodes. All of the bits of grenade go flying out in all directions, conveniently creating space as they go. All the little pieces have mass and mass gravitationally acts upon other mass, so they would very much like to come back together again. But since those pieces have mass they also have inertia and velocity and want to keep going the way they are going. Gravity is a very weak force and decreases exponentially over distance but velocity - momentum if you like - doesn't, because there are no other forces in play to change the inertia. So the bits keep on going, just like the Duracell bunny. No big crunch any time soon.

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So this universe with nothing but a hand grenade in it had no space in it either, until the explosion caused bits of grenade to go flying in all directions, creating space as they go? Are you saying mass or energy creates empty space around it as it "goes"?

I was offering nothing more than an admittedly simplistic (and not a little bit facetious) model of the expanding universe, since the OP question was about why gravity is not slowing down expansion. These questions are usually followed by "but what is it expanding into?", so I threw that bit in for good measure.

The universe is as big as it needs to be and always has been.

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This is not an idea to be tossed aside lightly - it should be thrown with great force