Dark matter and dark energy are not "things" like we're used to in physics. They're error terms phrased as though there was no error. We don't know the answers to your questions.
When you do calculations in cosmology, based on our known universe, made up of matter and energy, you get results that disagree with the observed data. They just don't line up, suggesting that our current understanding of the universe is incomplete (shocker, I know!).
It has been observed that if there was more "stuff" that acted something like matter, and there was more "stuff" that acted like energy, the equations line up with empirical observation better. So, for all intents and purposes, science assumes that there must be more energy and more matter out there in the universe. We're just having trouble observing it. It's kind of an application of Occam's Razor to the problem.
This "stuff" has been called dark matter and dark energy because we believe it is there, based on our observations and our equations, but we have seen no direct evidence of it.
We can't say how it behaves because we've never observed it. The perplexing part of it is that we simply don't know what it truly is, so there's no way to say exactly how it acts on the universe, other than in an "energy-like" way.
I believe this is comparable to the Lorentz transform from the early days of relativity. We knew from experimental observations that Maxwell's equations were not perfectly describing the behaviors we saw, and the Lorentz transform was a mathematical fit which corrected for those observations. We could say how it behaved, but we didn't know why. When Einstein proposed that spacetime warped, it showed a very simple rationale for why we saw the effects of the Lorentz transform.
In the world of cosmology, we're between those steps. We've seen the mathematical model which solves our problem, and it involves tweaking some factors -- mass and energy. We are still working towards a rationale which explains why these effects occur.
