If H +H cant get rid of energy would they be stable ? H2 is stable, so maybe you are right they lose energy via low level photon emission resulting in very low level radiation throughout all of space.
An interesting thing about H2 being hard to detect, it is a candidate for dark matter. https://principia-sc...tation-anomaly/ which might make Verlindes entropic gravity which I favour on occasion and MOND theories a little tenuous, and amusingly might also call into question the Hot big bang.
You seem to be confusing two things: the thermodynamics and the kinetics. The latter is the route by which bonding and energy changes can take place, during a chemical reaction. I've already explained hydrogen molecules can easily form, if there are molecular collisions with third body molecules to help carry off the energy that is released. The paper I linked to focuses on that.
So yes H2 is thermodynamically stable, but you need a kinetic route by which the reaction can go to completion. Part of that is solving the problem of how the energy is carried away from the newly forming bond, so that the atoms don't just bounce apart again. What I suspect is that they still need these 3rd body molecules to do this and so the rate of reaction in interstellar space will be very low, as only when, by chance, you get 2 atoms plus a "chaperone molecule" together at once will you get a successful reaction.
But of course the universe has billions of years to do this, so I am not saying it can't occur: evidently it does or we would not have the molecular clouds.
I'll leave the entropic gravity stuff to you, as I'm not sure I understand it.