I think you got a little confused with your wording there, which in turn has left me confused, but no matter.
What I mean was, and correct me if I'm wrong, but I believe Luke was actually struggling to overcome the Emperor's dark influence, in that respect he would have in fact being futilely attempting to use the light side, not the dark
I was under no such impression. Luke's struggle to overcome the Dark Side was during his brief duel with Leia; during the battle on Byss he fully intended to use the dark side powers Palpatine had taught him to destroy him. Fight fire with fire, if you will. He felt it was necessary that even if he could never be redeemed, even if he had to die in the end, he had to kill Palpatine by any means possible. 👆
In their second battle, Leia helped Luke break free of the dark side, and he realized that he was wrong. Fighting fire with fire was not the answer, and he went on about how the way of the Jedi was not a solitary path, etc. etc.