Phizzy
Dark matter and Dark energy, are not really understoood at all
Yes
there are no real "fixed" Laws of nature and Physics etc,
No, constants are still there fixed e.g. speed of light, E=mc 2 , etc. CERN and satellites are getting additional info plus discovering new things like recent Higgs boson. Bottom line: we're getting more and more sharper understanding of how it all works; this means new layers of physics mathematics .
long established thought that there is a finite quantity of energy in the Universe
Yes, conservation of energy and matter laws are still fixed and working fine i.e. no net loss of energy or matter, universe is still a closed system in this regard.
expansion of the universe may go on for longer than once thought
Yes, we know the universe will never recoil, i.e. stop expanding and bounce back. So no bounce back crunch.
It's all very exciting!