Power Steering tank is not under pressure, JB weld should hold. You may be able to find a replacement on Ebay for just a couple of bucks. Radiators are under pressure and I would leave all structural repairs to a professional radiator shop. They can do wonders, but can they do it for considerably less than the cost of a new radiator, I don't know. $160 for a radiator doesn't sound too bad to me. You'll know it is, well, as good as new!
You can fix an old radiator, but there's no guarantee it wouldn't develop another problem shortly thereafter. For example, if you had one leak in it and you fixed it, you now effectively raise the operating pressure back to normal, and the next weakest spot in the radiator may fail. You take your chances, sometimes you luck out and sometimes you wasted your money and end up buying a new one after all. Personally, if it's not some ultra rare or expensive radiator, I usually buy a new one for my own vehicles or recommend a new one for others for the reliability reasons above.
ASE Master Tech
20 years of automotive repair & modification, USA, Asian, Euro, old & new cars.