There are lots of interesting questions about what this would really mean, but it wouldn't break the FTL barrier - it's really taking a shorter path, not taking a long path but going faster.
This potentially raises paradoxes etc, and may also be impossible, but it doesn't break the barrier in the above sense.
Barring significant new physics, nothing can travel faster than the speed of light. And that's really a very probably no - although you see popular science stuff written like it can solve the problem, it doesn't, and we have no real expectation that anything will.
Dark matter, if it is matter (and there are good but not totally confirmed reasons to think it is) is just that...matter. It would really be not that special at all, except that it doesn't interact electromagnetically, but this doesn't particularly have deep implications - we already know about particles like that, neutrinos, but they happen to be lighter than the ones that would make up dark matter.