There's no work/life balance you can strike that will satisfy a woman. If you're busting your ass trying to support your family they'll whine that you never spend time with them. If you take it easy at work to make to make time for family they'll consider you a lazy bum that won't support your family. It's better to go your own way and optimize your work/life balance for your own goals.

she's already fucking some rando on the side

Yup. You show me a woman who has a "low libido" and I'll show you a woman who's a dirty nasty slut for criminal thugs but an ungrateful bitch to the guy who financially supports her fat ass.

Any woman saying that is the biggest red flag, hammer and sicle level red. At that point if you are lucky and live somewhere where you are not entirely fucked find hard evidence she is cheating and ruin her before she ruins you.