Radiator blow out

I have a 2000 Jimmy SLT with 100,000 miles on it. It is the small V6 engine. It has always run about 200 degrees with no problems. I took it in to have the cooling system flushed because the manual says to at 100,000 miles. I noticed that it ran about 210 degrees after I had it flushed. I checked the coolant and it showed it was good for -5 degrees. We usually need protection to -40 in Colorado. I don't know what that makes the boiling point but I am sure it lowers it. I took it back to the dealer and told them it needed more antifreeze in it. They checked it and said it was good for -45 degrees. It continued to run hotter than usual and when we had some 100 degree days the radiator blew out. I took it back to the dealer and they said that they did not cause it and it cost me $600 for a new radiator. They told me that my intake manifold was leaking and my water pump were leaking and wanted another $650 to fix them. I told them to fix the radiator and nothing else. It has been over a month now and my water pump and intake are fine and not leaking a drop of water. The temperature is running at 200 degrees again like it used to. My question is did the low mixture of antifreeze cause the system to run too hot and blow out my radiator?