应该是：
1 When he was a boy,Pele had a dream.------when搭配“一般过去时”.
2 Ever since he was a boy,Pele has had a dream.-------有 since 的参与,你必须用“现在完成时”.
3 While he was a boy,Pele had a dream.----- when搭配"一般过去时".
4 He SAID that he HAD HAD a dream SINCE boyhood.-------主句that 句子（since +过去完成时）
5 在你的语境中,when和while的使用没有区别.