Yes, you're on the right track. Although I do not believe in the big crunch, I would like to point out some things.

Time is not the force expanding our universe. The expanding force is Dark Energy. Dark Energy expands the universe further as time progresses; thus, time is necessary for expansion. The big crunch is highly unlikely for different reasons though. Our universe has a set amount of matter and energy, we cannot gain or lose any without the help of wormholes (which aren't big enough to transport enough gravity to prove this wrong). If we converted everything into gravity, space would shrink. None of it would disappear, but the point of where the gravity is most powerful will shrink the space, causing the outter edges of space to come a little bit closer to the source of gravity. But, gravity is oddly weak, according to M-Theory. It's working on 11 dimensions, providing only a fraction of it's power to our third dimension. Thusly, it is not powerful enough to compensate for the incredible rate of expansion enforced by Dark Energy.

What if the gravity is pulling on the edge of the universe directly? Not possible for two reasons.
1. Dark Energy expands our universe faster than the speed of gravitational waves, so gravity can never catch up, even if the source was right at the edge.
2. The edge of space has no mass, thus, gravity doesn't emit work upon it.


Gravity can only affect the edge of space indirectly, by doing work on the innards of space.