What is the cheapest way to live alone?

I'm not sure how to write this in a way that will get the advice I'm looking for, but I'd like to do my best. I'm sorry if it comes as off as strange. I think if I ask for advice without giving enough context, it will be treated like an X/Y problem, but if I give all the context it will be treated poorly because my situation is awful. But I will give as much context as I can and hope for the best.

I live in Japan with permanent residency. I've lived here since high school and have no family in another country. I speak and work in Japanese. I'm in my early thirties with a child and have a good job where I make ~7,500,000 a year working from home at ~40/h per week without overtime. I am my family's only income. My wife is disabled and unable to work. It is enough to save and make stock investments for retirement, but obviously nothing amazing. I have plenty of savings to work with. My family's stable financial situation is the only thing I can say I am proud of.

I am autistic and over the last several years, I have failed to maintain a successful relationship with my family. At this point, it is clear that living together is only harming them. I want to continue to support them and live close enough to regularly visit my child, but I am unsure what the best way to balance it financially would be. Until now, I've never had to take care of any finances by myself and am completely ignorant of how much living by myself would actually cost. I am afraid that by separating and adding additional living expenses to myself, I will just make things worse by also ruining our financial situation.

What would be the cheapest way to live by myself without being literally homeless? I live in Hiroshima. I don't care what I eat. I don't play video games or have any hobbies that requires space. I don't own a car. I just work, spend time with my family, and sleep. As long as I have basic internet, my computer, and all my basic needs met I will be satisfied by myself.

The only three feasible ideas that I have right now are:

1. I think I can get a very small apartment for ~２万 a month, but what are the minimum expenses typically associated with that? I am afraid that it might be surprisingly high and I end up being unable to effectively continuing saving money. Less importantly, my wife will likely want me to live not so close to them, so I will need to either spend significant time on the bus to visit or buy a car, both of which make this choice my least preferred for selfish reasons.
2. When I was in university, I lived in my car and it was very cheap. In that form, it wasn't a sustainable lifestyle, but I see lots of videos about van life in Japan and it seems like a quality of life that I could be happy with if I spent the money up front to do it right. I have the same worries that it will have recurring costs that I am not predicting, but this honestly seems like the best fit for my happiness when I imagine it without knowing anything about costs.
3. By divorcing, my disabled wife would have additional support from the government made available to her, and a little more on top of that because she would have custody of our child. However, such support would stipulate that she sell our house. Additionally, it seems at least legally gray or even illegal for her to claim this money if I were to continue to financial support her, yet not supporting them would net a significantly lower QOL for them while leaving me with more money than I would ever need. Additionally, downgrading my family's home and potentially changing schools would cause significant mental/emotional to both of them. Unless I am misunderstanding something, this is the worst option.

I would be very grateful to get any advice. I am scared of making the wrong choice and ending up regretting it.