The dialogue is canon. Malak states that he was using 'all of the power of the star forge'.
When did he say "All of the power of the Star Forge"? I remember it saying the Star Forge boosted his abilities, but it was never specified by how much. You *can't* quantify the boost. And even if he was using "all the power" we don't know how much *all* is.
When you see Malak draining energy from captured Jedi, then stating that he's using all the power of the Star Forge. Kreia is obviously a dubious source, as she's trying to manipulate the Exile, but I doubt that Malak would lie point-blank during the most heated battle of his life. What would that accomplish?