I don't think her concern is just about him ridding himself of her, though. Before that concern, there's his body's breaking down specifically because of all the work he puts in to support both himself and Saitou.
You've got it backwards here. Her primary concern is being abandoned. There's a whole history of abuse, abandonment, and neglect she's working here. Her primary concern in all of this is being such a burden she'd be abandoned. After that comes the continuing toll on his body, but even when they talk about the issue, it's always in the context of her being abandoned. It's not that she doesn't
care, but rather that she can only contextualize it fully in terms of whether he keeps her or not.
You'll remember she couldn't stop going into hysterics about being hated and abandoned the moment he started peeing blood.
Again, not because she didn't
care, but rather, because those are the terms she can fully grasp the situation under.
On one hand, I don't think it's safe for Yokoi to not still actively evaluate "will saying this make her kill herself" with every conversation-- the "Stress" arc was all about him not doing that after overestimating her progress,
He didn't overestimate her progress, for the record. I know it's been a while, but he just lost his patience: He was thoughtless. Had he had the presence of mind to consider her condition, he would have evaluated it like that.
On the other hand, the groundwork was already made in this chapter's conversation for Yokoi to reject the idea of doing sex work. They already acknowledged that it was taxing, and Takamatsu in particular was none the better for taking it up. I agree that he totally could have shot down the idea without issue.
It's a recurring theme where her outbursts are caused by him not setting honest, clear boundaries. The Stress arc started when he said he didn't like something, and instead of explaining precisely how small of an issue it was for him, he left it at "Yeah, I don't like this", and left it all to her (very Autistic, and very negative) interpretation. So "Yeah, it's not my favorite thing" got turned into "MY HEART.IT BREAKS WHEN SOMEONE PUTS ME NEXT TO SOMEONE ELSE! AND I HATE ANYONE THAT WOULD DO SOMETHING SO AWFUL TO ME". Obviously you would realize that Yokoi is annoyed by the act, but doesn't find it to be a huge deal. Obviously you realize that he would appreciate your not doing it, but wouldn't hate your guts if you did it every so often.
You'd realize it, of course, if you weren't moderate-to-severely Autistic, and dumber than average. She is both of those. What she needs, and has needed more than anything else, is boundaries.
When she asks if it's ok for her to do sex work, a clear, honest answer is more productive than whatever this calculus is.
When she worried about you abandoning her, a clear, honest outlining of the thing she'd have to do to make you abandon her helps more than "Naw, it's fiiiine, you do whatever". His concern that she'll interpret his answers on the matter to mean he'll leave arbitrarily is accurate. Acquiescing to her every hypothetical like this is counter-productive.
And by God, when she's worried you hate her, it helps to explain how you feel. Not knowing what people think, and how they feel is, like, the whole issue with Autism in the first place. Just explaining himself and making up on the spot would probably do wonders to avoid panic attacks.
She works best with clear, predictable rules to follow. Stress only happened because the rules that had been set were violated by Yokoi when he snapped at her questions.
