I don't know, but they seem to work okay for me.
The engine will take much, much longer to warm up. In the winter the engine may never warm-up. At best it's a short term band-aid.
Nothing at all. You are removing a valve that is already wide open when the car is overheating, so it makes no difference.
Yes, we are glad you fixed it. It's nice when advice is followed and (most importantly) it works. It may be that only one piece was failed now, but the rest would have gone soon too. Now you won't have to worry about it for a long time.
Now onto the rough idle. Can anyone say coils and plugs?