“Meaningless” is vaguely defined here. You defined free will at the beginning, so it must have some meaning in that sense.
It seems like “meaningless” is actually a placeholder for “doesn’t really exist”.
Which would make the trilemma boil down to:
Free will doesn’t exist
It exists and I have it
It exists and I don’t have it
And your basis for rejecting point 1 is that “truth wouldn’t matter, anything would be justified, therefore it’s false”.
I don’t think this follows.
Ultimately, what you’re pointing out is an issue of distinguishing between a non-free operating system that tends to accurately believe true things, versus a confused non-free operating system that tends to believe false things.
Just because this distinction cannot be subjectively resolved with 100% confidence (because what if the axioms of logic and self-coherence are wrong?), doesn’t make this automatically “moot”.
You have to at some level assume logic, memory and a degree of rationality no matter what circumstance you’re in. If you don’t assume that, then you’re not free either, you’re just acausally operating based on random whims—and that’s something you don’t control by definition.
“I don’t find this tasty” is not the same thing as “my body doesn’t tell me it’s good”, and this concept is at the core of many suboptimal fad diets, as well as a common blanket justification for being fat and unhealthy.
If you eat Krispy Kremes and pizza exclusively, your body will “tell you it’s good”. The whole reason people get fat in the first place is that the taste and satiety mechanisms we’ve evolved in an ancestral context are maladaptive for the modern hypercaloric, hyperpalatable environment.
If you eat donuts and burgers, and take a multivitamin to avoid deficiencies, I’d challenge you to crush, chew and savour the multivitamin on your tongue and see what your body has to say about that.
By omitting vegetables and fruits, you not only risk vitamin deficiencies, but miss out on the most under-appreciated aspect of whole plant foods: their phytonutrient and antioxidant content. Plants have an enormous array of complex, immensely beneficial and poorly understood compounds which interact with our bodies in ways that invariably prove immensely beneficial.
You can handwave the ubiquitously agreed upon benefits of fruit and vegetable consumption as “reliant on correlational studies”, but this is a major handwave indeed, and includes ignoring the strong mechanistic bases to assume this is almost certainly true.
Fundamentally, the obesity epidemic appears largely due to a mismatch between the body’s evolved hunger and satiety systems and the foods that have been created to wirehead them. Therefore, using “my body’s hunger and satiety systems tell me that eating XYZ is good” is very uncompelling.