The Ancient Sith ressurected him? Yeah right...after Endor he possessed Jeng Droga and went to Byss to his clones. Until Empire's End, the Ancient Sith hadn't seen him in ten years.
Sorry to ruin your party, but...
After his spirit was resurrected from the netherworld of the Force by the Dark Lord ghosts of Korriban, Palpatine took possession of the body of the Emperor's Hand Jeng Droga
Exertion would be using it...having it reflected in your face is it 'backfiring'...and again, lightning in your face doesn't change your teeth, hair,, voice, eyebrows or turn your eyes yellow. Mace meant to capture him and was menacing him with a saber anyways. Which was suicidal to the extreme as it was
Actually, Exertion can expand to a great deal of things.
Backfiring? Dude, not at all.
Suicidal? It seemed Palpatine f*cking with Mace was Suicidal, because he got overpowered.
Of course the Dark Side energies twisted his Avatar, but HIS FACE MELTING was a product of Lightning.