Work 9-3 and pick up a hobby. You only need to outperform your peers, or train them up if that's possible. Beyond that you owe the company you work for nothing.
Why work harder, when working harder provides you no benefit whatsoever?
However, I know that if I worked 9-3 my personal well-being would improve.
You only need to work as much as whats required, nothing more. If you can close off your assigned 'tickets' etc, given each sprint, do so, then rest. Your personal well-being is #1.
Getting paid for time is a trick that you need to surpass. Get paid for what you produce. That is the primary difference between businesses and individuals: the non-correlation of time and revenue for a business versus an individual.
Are you making 7 figures? If not, you shouldn't feel guilty about how much you're working. It sounds like you could lean on your employer for a six figure raise which can pay for things like a personal trainer.
More importantly, this is my fav career anecdote:
"You know you've made it when people pay you to be you."
It sounds like you're at (or past) this point. The hours you work don't matter. The value you bring to the company, and the value the company brings to you - that's what matters, when you reach that point.
Personal well-being is one of the things that the company can give (or take!) from you.