I think if he did kill Palpatine, he would have fallen or come close to it. So Anakin may have saved from being an agent of the Dark Side. But I don't think Mace would have fallen. His will is too strong. I believe his use of Vaapad gave him a resistance to the influence of the Dark Side. But not many Jedi could engage Palpatine in a duel without succumbing to the darkness. So that is a testament to the will that Mace Windu had.
He wouldnt have been able to.
Palpatine was bending his lightsaber with his force lightning. If he really wanted to, he would of blown Mace to dust. But that was a key moment in Anakin's fall.