Humans will never be able to manipulate space. I don't think space has an actual "fabric" that you can manipulate. The fabric of space time is probably like the sky. Its there, but not a literal object
Gravity isn't strong enough to use it to travel anywhere. Maybe when going to Mars, but not Star travel
If wormholes exist, if you were to travel through one, there is no way to know where yo will end up. It could be another galaxy, time, or maybe a different Universe.
I love the ion drive rockets, but to get to the stars, and back, we need to go faster than that. We need to go faster than light.
Since the only thing we know that travels at the speed of light.....is light, we should manipulate light. Sounds crazy...but so did blackholes 30 year ago. If we can speed up light (we can slow it down) and since light has mass, we should be able to put a micro probe on a light beam, speed the probe up, which would speed the light up, which would take us almost anywhere in the galaxy at the very least.