I don't think I can quit until next year, due to the "job hopper" label - I've only been here for six months.
My health has definitely taken a downhill turn... before I was at the gym 3/4 times a week, plus bike rides. Now it's one or two, and that comes at the cost of being able to do other things.
Start looking for another job ASAP. Raise your salary expectations to at least 10% over what you make now. Name a figure at least 15% higher early in negotiations, if you get cornered in to picking a number first. Consider going higher than these minimums. 20%. Maybe 25%. Don't drop your starting bid until you've failed to land at least two jobs due solely to salary expectation mismatches.
You may be surprised at how accepting people are of a slightly-nicer-worded version of "why do I want to leave so soon? The job is shit, that's why", especially if you can frame it as "it's not advancing my career as I expected blah blah blah". And really, six months isn't that bad. I know lots of very successful people with multiple entries like that in their work history.
Since you can't really use anyone where you are now as a reference anyway (not for this particular job search, at least), if you haven't already been explicitly told you have to work 10-12 hours, consider cutting back to 8 hours/day cold-turkey and using the time you save to recover and to look for a job, at least until someone complains.
(I'm assuming you're in tech and don't live in the middle of no-where. Hell, I do live in the middle of no-where by many people's standards, and anyone with even a hint of talent gets snapped up here fast. Job openings as far as the eye can see. It won't last forever—move while you can. It's musical chairs.)
Being at one job for a short period doesn't make you a job hopper, rather it is about the long-term pattern.
You can honestly say to potential future employers that this job is just a poor fit. Better to cut your losses early (and save your health) rather than tough it out for something others may not even care about.
My health has definitely taken a downhill turn... before I was at the gym 3/4 times a week, plus bike rides. Now it's one or two, and that comes at the cost of being able to do other things.
I definitely agree with this article.