As space expands,it releases stored up gravitational potential energy,which converts into intrinsic energy that fills the created volume?

The universe isn't actually expanding at all. The idea that it does comes from the original misinterpretation of galactic redshifts as being a doppler effect when, in reality, they are a scattering effect. The galaxies are not generally receding from each other. Their light simply loses energy through it's interaction with the molecular hydrogen that fills intergalactic space (see source).

If space expanded, as well as stretching out the energy of light radially causing distant galaxies to appear redshifted, it would stretch it out transversely causing a reduction in their surface brightnesses. This is not what we observe:
http://www.sci-news.com/astronomy/science-universe-not-expanding-01940.html

Expanding space would also stretch out the light curves of quasars (their oscillation in luminosity). No sign of this either:
http://phys.org/news190027752.html

There never was a Big Bang. This documentary may enlighten you:
https://www.youtube.com/watch?v=IFFl9S39CTM

I don't see how anything can be infinite when we are so obviously in a quantum universe.

Potential energy is not infinite. Therefore, it does not expand without limit.

I personally think (and I'm probably wrong) that there ae tiny black holes in the universe. Einstein would rotate in his grave if he heard the modern astrophysicians talking about dark matter. There IS as sourec of gravity we don't know about, but it can't be dark matter, it must be something else.