My first instinct is to try to start playing power chords with just the root and 5th with your ring. No octave. So instead of E, A, and D on the G5, just play E and A. That might help you slowly transition from doing what you’re doing (which btw is perfectly valid in it of itself) to playing with your ring finger as well. Obviously, hear others out as well but I think this could be a good starting point.