I believe you read the table backwards on #1. Cold iron, silver, etc. do not bypass DR/magic unless they are also enchanted. It is an enchanted weapon with +3 or higher equivalent that can bypass DR/silver or DR/cold iron. For example, any +1 flaming burst longsword, even if it is just made of steel, will bypass a werewolf's DR.

I don't think that your assumption is implied, exactly, but I can see how it would be inferred.

Also, to clarify something that the previous answerer touched on, but didn't make explicit, there is no real connection between any creature having DR/anything, and being able to bypass DR. The ability to have DR/magic, for example, and have attacks that bypass DR/magic are two completely separate abilities. A creature can have one, without implying or necessitating the other in any way. This is why DR/- doesn't grant any sort of ability to bypass DR, not simply because it has DR/-.