If the portion of the text
"It only increases your manifester level, which helps you overcome power resistance and increases the duration and other effects of your powers."
Is taken much more strictly and were written (or just read) more like this:
"It only increases your manifester level for the purposes of overcoming power resistance and increasing the duration and other effects of your spells."
I think we would be okay. That way it explicitly states what it covers rather than using a term that has been applied to many other cases (as you mentioned).