Hi Finn. I came across this post and your games recently. Life & Lemon has potential. The other games also feel emotional and nostalgic. They showed me a ray of hope that you will definitely make a nice game. However, since your question is about quitting your job and aim for a commercial release, lemme throw in my two cents.
One of the way you can consider is, not quitting your job right away but go interview somewhere, probably some remote company. Once you get the offer letter, if i remember correctly, you have 45 days of notice period in which the work should be lighter than usual. I think you may use this period to work on your game. If you're lucky, you can ask for a couple of weeks later in your start date for more time.
This suggestion arises from a possible concern that the burnout after quitting a bad job is no joke. The exhaustion (and possibly depression) could be so intense that one could do nothing other than sleeping. Touching the keyboard could trigger trauma and mental numbness, let alone programming. The long-term natural cure is, of course, to take a long time to recover. However this may lure one into a tricky psychological trap to procrastinate on job-hunting, raising barrier to the next job.
Another possible concern is that making a game without financial backing could be tough. Thankfully you don't have to worry about living expenses in a couple of years. However firstly, the expense for idea and inspiration may be limited, e.g. to go on a vacation for idea, or to buy an art-book for reference, having to check the account balance every time is uninspiring. Secondly, the self-impression that *you are enduring* is there. Having a productive day may ends up in no reward, having a bad day may ends up in rumination, it's a losing game without an end if this psychology is not kept in check. You fared well enough on your job Finn, this labor of love is supposed to be a reward for that long-time enduring. Setting a "new-job" line (don't read: living-line) could be a trick to make yourself focus on the game. Without "other" things. Well, except for some cups of lemonade.
Hope you the best enjoyment on your labor of love and a better working environment on your next job. Life is mysterious, corporate greed is not, this makes life is a fascinating place to explore and experience. Mysterious Voyage, Be of Good Cheer! (lol)