What I meant by wiggle out is after Marth Uthrows you can recover and shine before he can grab you if you are fast enough, Ive seen it done. Not at certain percents though, I think you need to be above 20 for it to work, although for frame perfect control it could maybe be sooner. And yeah escaping a grab with enough button presses could be done at zero I think, however against a frame perfect thrower it would be different anyways.
Also infinite ledge stalling is banned in tournament play isnt it? So that is not a viable strategy, thus once again lifting Fox to the top. However I beleive that a perfectly controlled IC could maybe beat fox because damage against nana doesnt count, you could have her cover you at all times and vise versa with perfect pivots and such.