For your resistances between 3v3 and gnd / 1v15 / 1v8, were those readings 16.3 ohm or 16.3k ohm? If they were just 16.3, that would be indicative of a short. It also looks like your resistance between 1v15 and gnd is low (assuming it really is 1.9-2.5 ohms). That's almost a dead short, and could potentially messing with the power to the CPU / GPU, potentially leading to your issue. I would try resanding the edges of the Wii, see if that clears up any shorts.
What grits of sandpaper did you use when you first sanded your board? You should be using 120, 220, 320, 400, 600, 800, and 1000 for the best results.