Evening is pretty much make dinner, eat, relax for a bit and be in bed reading by 8.
But otherwise, it prioritises your side project while you're fresh in the morning and puts relaxing (movie/TV/etc) for when you're fading at the end of the day.
even if you assume this is possible, why would your boss pay you for the 8 hours when it clearly is possible to only pay 6? You end up back where you're started.
The issue here is that the income you generate from your job is not enough. I dont know what the solution is - but under a capitalist world-view, the only solution is to own more capital, get that capital to produce your income stream (dividends or capital gains or whatever), and thus, give yourself back time.
AKA, this is called retiring, and if you can do it early, you end up with a better life, able to spend your energies on activities you care about (such as making this game).
Which doesn't necessarily change the point, but I'm not sure what if anything the point is supposed to be, and it seems an important omission.
I might have 2-3 hours each day (of energy and motivation) to work on projects but not 8. Of course I never have 4 hours during the week either, I'm lucky to get 1 in usually.
Saturdays and Sundays are chore days, or family days, or simply resting, or ...
About 4h remaining for yourself is still fairly realistic.