This is so unlikely that it's not worth changing so much of your behaviour for it.
Don't forget the decrease in your sense of self-worth and increase in being cynical and toxic to deal with.
People intentionally doing the bare minimum are unhappy unpleasant people. People no one wants to associate with.
And even if you’re right, there should be some nontoxic people in toxic environments and they should able to talk about it without someone immediately accusing them of being the problem.
OP admits to wanting to "teach the company a lesson"[1], and then responded to another commentor, who advised they fake a personal crisis and play victim and referred to women as people with "oily holes between their legs", that this was "interesting and worth implementing"[2].
1. https://news.ycombinator.com/item?id=32970777 2. https://news.ycombinator.com/item?id=32970399
I know you're mostly focused on OP's use of the word "honest", but I think that misses something.
The term "reasonable best effort" is biased in favor of the employer since companies recognize that mediocre performance (relative to the position) is the norm. They also recognize that people like OP exist, and are more than happy to take advantage of them since they aren't likely to aggressively negotiate for what they're actually worth (and actually get it), and that not everyone has the luxury of just switching jobs to not get overly exploited. It's also tricky because things change over time, and what once was fair or mutually beneficial may no longer be, and by then, it be can be tricky to transition out of that.
I do think OP needs to reflect upon why they stayed at this place if they've felt taken for granted for so long. At the same time, I understand the frustration and sense of futility that comes with feeling like you want to give your best, but that you're not in an environment conducive to that.
I also don't think honesty is so binary to where if OP scales back effort in order to transition out of this role, that they can no longer claim to be "honest". Nor does honesty necessarily imply putting oneself in a precarious position and quitting before they're able to do so, especially since I doubt OP's higher-ups have any expectation of being honest and transparent with them that their days are numbered regardless of performance.
edit: I didn't see OP's reply to other commenters and assumed good faith. Nonetheless, I stand by my comment even if it no longer applies to this particular situation
Your sense of self-worth will be impacted. You will become the toxicity you hate.
Either do a good job, or leave for somewhere else where you can. Anything else is not the activity of an honest and passionate person. You can rationalize all you want, some things are out of your control, but the one thing solely in your control is how you behave. Staying on a job doing the bare minimum until you get fired because you've decided that the effort involved in improving your situation is "not an option" is a choice, and not one that reflects well on you.