The same as you, I say "No" to the lack of conservation of energy but for a slightly differnt reason. I'm also opposing the math but only the part that is based on an assumptions that the mass we see is all that is there.

I also know (which you might have missed) that it may lead to a result that the universe is expanding and to another, that because of this the energy is contstantly created. The latter result isn't so widely advertised so it isn't generally known unless to mathematical physicists, who exchange the information only among themselves. Which I consider wrong since I think that knowledge of no aspect of Big Bang should be kept only to specialists and so neither the fact that the Big Bang requires constant creation of energy.

If the density of the universe were really (6.0+/-0.5)x10^-27kg/m^3 (as indicated by present value of Hubble constant (70+/-3)km/s/Mpc) then the accelerating expansion of the uiverse could be explained as an illusion just with Einstein's gravitation and the principle of conservation of energy. It would then contradict the hypothesis that the cosmological redshift is due to the Doppler shift.

Furthermore the illusion of expansion includes also the acceleration of this expansion in the amount that is observed within accuracy of observation, and the Big Bang hypothesis so far can't explain it without introduction of unobserved phenomena ("dark energy"). Which would mean that Einstein's intuition about the universe migh have been right.

Of course, lack of real expansion of the universe, besides showing that there was no event like the Big Bang in the history of the universe, requires explaining a lot of things that till now were explained with the Big Bang hypothesis. But it maybe even more fun than looking for the "dark energy".