The pot you linked to offers a hole drilling service. I said in another post, I think, add a weldless ball valve to drain the whey, the way professional do, and then you won't have to move the curds around. As for heating you could use a silicon heating blanket, but that might be expensive, I would guess about $200 - $250 as I've priced them for other applications and they go by the square inch. If I were you 20" is not that wide, just goto Target, scrap metal shops, anywhere you can think of and find a pan that big that's at least 6" tall. Then put 1" spacers on the bottom so the pot doesn't touch and use an outdoor burner, think turkey fryer (the end of the season is upon us and you should be able to find one cheap on sale or used on craigslist), and heat it up that way. I would insulate the rest of the pot that isn't in the water bath with some of that aluminum bubblewrap they sell at hardware stores to wrap air ducts in. I use it all the time to insulate kettles I'm Boiling.
Link to weldless ball valve http://morebeer.com/view_product/19793//Weldless_Spigot_-_Stainless
P.S. I was just thinking if you could find a used jacketed vat (tank) for wine making, that would be perfect. Then it has dual purpose you could use it for wine as well, less yelling from the misses.
On that note you could also do what some wine makers use when their tanks are not jacketed they use an immersion plate, seen here http://morewinemaking.com/view_product/19738//Weldless_Wine_Cooling_Plate_Kit_-_10.6in._x_24_in
. or use a cooling snake, same principle but more expensive. Use your imagination, just get like 8 feet of 1" flexible food grade tubing and hook it up to a fountain pump or cheap pump from harbor freight and put it in a large 33 gallon rubbermaid (hard plastic one) and then put the heating element in there and have it pump the hot (warm) water through the tubing and back to the reservoir, while the tubing is in a spiral coil in the pot.