None of that is particularly relevant to why Swedish people are good at speaking English. It is far more to do with immersion and affinity with the culture and television, as well as the quality of language teaching.
All that is true, and Swedish kids learn English at a really young age (both formally, from watching TV and from exposure through all the other outlets that use it) (Finnish kids are learning English in their first year at school now - from age 7)
However Swedish, Norwegian and Dutch are all pretty close to English in lots of ways - word order, "past words" ending in d or t, possessives adding an s etc.
In my experience Norwegian and Danes often have the easier time mastering an 'English' accent, Swedes really struggle to lose the sing-song.