The nuclear fusion taking place inside the stars opposes its gravitational self collapsing force. But, how does physicists calculate it? I just know the classical gravitational theory and not a bit of general relativity. So, I would like to take the situation in a classical way. For example, in terms of Lyttleton-Bondi Model for the Expansion of the Universe the expansion of the universe is explained if matter has a net charge. Imagine a spherical volume containing un-ionized atomic hydrogen gas of uniform density. Assume the proton charge is $ke$ (where $e$ is the charge of an electron (this situation is taken for net charge of matter)). How to calculate the gravitational self collapsing force of this so that I could calculate the value of $k$ for which the electrostatic repulsion opposes it and the volume doesn't collapse on itself? I know how to calculate the gravitational force between masses or simple shapes(found using integration). But,I have no idea on how to calculate this.
(Even though Lyttleton-Bondi Model for the Expansion of the Universe model is discarded I would like to proceed with this as I don't know any high level math or other theories except classical mechanics taught in high school).