Wilful control of reality in this case requires truth to be subjective

Hmm, maybe. Others have covered this and it doesn’t quite seem perfectly true, but let’s let that slide.

and conversely, if truth is subjective you can control reality

No, that definitely doesn’t follow. If truth is subjective it doesn’t at all mean you can control it. It just means that what is true for you might be different from what is true for me. The reason that’s the case isn’t a part of that equation.