There's no "figuring it out." Fusion waste isn't radioactive. You can't do radiolysis with it.

There's a difference between radiation and radioactivity. Heat and light are radiation. Radiolysis requires radioactivity.

It's not "more efficient" to take hydrogen, apply fusion to turn it into helium and generate power, and then use that power to "split" water molecules.

You already have the hydrogen from doing the electrolysis. The closest thing you could do is capture the power generated by the fusion and convert it into electricity, and then use that electricity to do more electrolysis. I'd have to look at the specific numbers to calculate loss, because fusion is weird and generates enormous amounts of energy, but it also isn't captured with 100% efficiency. And besides, it takes power to run the fusion reactors, which is currently the main hurdle in the way of running it at scale.

If you're in a space colony though, water is too precious to be splitting into hydrogen and helium. You would probably just get your hydrogen directly from a gas giant instead.

Otherwise, light and photosynthesis will basically always be the most efficient to grow calories for sustenance.

So we've come full circle, and you've admitted that nuclear fusion cannot generate calories. Great.

You also continue to ignore macro- and micro- nutrients. Dietary requirements are more than just "calories."

Lastly, aside from aneutronic fusion being hardly more experimental than it is theoretical, that's a complete red herring and has nothing to do with what we're talking about.