1. I've never even played a peach, idk, maybe mix it up with some full hop bairs/short hop fairs (sparingly) and use dairs to safely regain some control of the stage and sustain a form of defense if something goes wrong??
2. First off, what has worked surprisingly well in my experience is stalling on the ledge until the opponent is in range for a fair or a nair to punish their punish attempts. On battefield, as mentioned before, experiment with the parachute under the stage and maybe try a uair. Otherwise, nothing comes to mind other than stalling and some mindgames on the ledge (again, actually works for whatever reason) and wait for an opportunity.
3. Experiment with jabs, try to play around with ccing after the first jab to squeeze the second one in faster, don't just d-tilt all the time, they can just shield and punish/get away. Mix it up with cced jabs, a short hop bair (make sure you input the bair very quickly to avoid lag time on the ground) and even some repetitive jabs. Also, I have not tried it, but reading rolls and even pressuring using the d-smash seems very effective in theory with the correct spacing (I don't see many G&W's implement this in their game)