问几个英文语法的问题In his memoir,Baker tells stories about the time b

问几个英文语法的问题In his memoir,Baker tells stories about the time before he entered high school,when he is having to deliver newspapers to the huge estates and mansions that lined the riverfront.这个句子里的about the time为什么可以这样说?不是应该at the time才对么?另外,is having to 有什么语法上的错误么?To the disappointment of the crowd,neither the president nor any of his aides were able to attend the ceremony这里的were怎么就错了呢?不是说neither nor后面的动词要就近么?不是离aides最近么?为什么不是were?As a freshman becomes adjusted to the routines and demands of college life,one may realize that the rigors of high school were good preparation.这里的one不可以这样用么?那么one真正的意义和用法是什么?另外这里的were不是与全句时态不符么?According to some demographers,the number of United States citizens aged 65 or older is likely to rise to 87 million by2050.这里的话,or older这样的表达哪里错了啊 不能这样说么?When Doris Lessing published the Golden Notebook in 1962,it instantly established herself as one of the most important literary voices of her generatons.这里的话我知道it不可以指代前面一件事情,但是它说这里it错了的话为什么不可以理解成是代指那本书呢（也就是那本书让那个作则得到了什么的荣誉什么的）