Given the RotS novel explicitly establishes Palpatine as the limit for Mace's Vaapad, with Malgus being well below that, there's literally no way for Malgus to win as Mace can match him in any aspect where Malgus is fueled by the dark side. It's a draw at best, but Mace being on par with Dooku or above in of itself gives him the win here.
The fear of Anakin wasn't even a factor until the end of the fight. Mace and Sidious were already fighting to an impasse until then.
Secondly, the idea of Mace being amped by the circumstances of his mindset is never explicitly stated in the text. It was an extrapolation that Silver drew by connecting two passages in the text, and alternate explanations have risen for why Mace performed the way he did. Mace's own darkness is only as relevant as far as actually using his form to its best capacity goes; the rest is up to his opposition.
What the text does say, though, is that Mace was cutting loose and that he was reflecting Sidious' dark side fuel, hence why he matched Palpatine perfectly (it's pretty coincidental that Mace having a random amp would make him exact equals with Palpatine).