You can cut the old pieces up into small chunks, fill a mold with them, and then pour white or cream wax into the mold, so that it makes a sort of mosaic candle. These can be quite striking. I have no additional wick information, everyone here has already posted what I know about wicks.
I second the milk cartons. Use half gallon or quart sized for large candles. You'd have to pay a good price for a candle this large at the store!
I have an old spaghetti sauce jar that I cleaned thoroughly, removing all sauce odor, label, and glue. Now I position votive candles in the middle of it, one at a time, with a pair of tongs. I light the candles, and the first one made a ring of scented wax on the bottom of the jar, with a hole in the middle. I put another votive in the hole, lighted it, and repeated. Now I have a clear jar that has several layers of wax built up, with a hole in the middle. I think it looks interesting, and I doubt that there are many like it out there. The wax is not really wasted, as some of the old wax melts with each new lighting, and it also forms decorative layers.