With regards to fast travel, you’re actually not that far off from something that was proposed in 2011 by NASA employee Harold White!
It seems there’s a bit of confusion about dark matter and gravity, though. The phenomenon we call gravity is really just a distortion of space and time. Both dark matter and regular matter interact in the same way with space; the more of it there is, the more space bends. Dark matter is five times as plentiful but impossible to observe directly, so we have less of an intuitive grasp on it. But both dark and regular matter warp space, and the more heavily distorted space is, the ‘stronger’ the gravitational pull is. It’s true that in places with a lot of dark matter, you also tend to collect normal matter (this is how we think galaxies begin to form). And while collecting a little bit of normal matter will increase the overall amount of mass in a given region, thereby deepening the pucker in space we’re looking at, neither the dark matter nor the regular matter are responsible for ‘causing’ gravity. The combination of both forms of matter are responsible for causing the distortion in space and time that causes things to feel a gravitational pull.
As far as we know, we can’t make dark matter do much of anything, since it seems to only interact with other things in the universe through its disturbing affect on space (i.e., via gravity). However, what you’re after with your proposed method of travel is, fundamentally, a way to distort space, compressing the part in front of you, and releasing it once you’re past. This is precisely what every proposed (mathematically plausible) warp drive is trying to achieve. Since you create an expansion of space behind you, as the image above shows, you can almost surf space-time on an artificial distortion.
The main distinction is that instead of proposing to bend space by moving heavy objects around, it’s more efficient to bend space using the energy equivalent of that mass. Space does not like to bend, and the math used to predict how much energy this would require had always indicated that you would need to convert a mass the size of Jupiter entirely into energy in order to make it work. (Jupiter, for the record, is 317 times the mass of the earth, which weighs it in at 1.9 x 10^27 kilograms.) Hauling Jupiter masses around with your spacecraft is hugely unfeasible, so this idea had been mostly discarded. This is why people got very excited about Dr. White’s modification to the math in 2011. He found that changing the geometry of the bubble of surfable space would drop the energy required to force the distortion by factors of many thousands and into the range of plausibility. He’s currently trying to design a miniature version in the lab to make sure that his idea can work at small scales.
For the moment, even Dr. White’s model is still science fiction. Even if it does work, there may be other tangles to work out - a few theoretical physicists have worked out that this kind of travel might trap high energy particles inside the warp bubble, releasing them outwards in a potential death ray when you arrive at your destination - not quite ideal.