求高人解答英语中一些插入语,比如"that is,as it were,that is,it is said”的用法.

求高人解答英语中一些插入语,比如"that is,as it were,that is,it is said”的用法.
我在雅思作文中使用,因为我的作文必须到7分,因此必须使用一些高级的用法,比如插入语,同位语等.问题如下：
1."...,that is,..."表示"即..."的意思,那么是不是其后必须跟名词性从句?比如On the first floor,that is,the floor at street level.或者Nicole was not dead,that is,he was sentto the hospital by passerby.
2.as it were表示,就像过去那样...,那么是不是在任何情况下,比如句子前半部分无论主语是单数是负数或者无论时态怎么样,此处一律写成as it were?比如The responsibility of protecting the environment is,as it were,with everybody.或者The guests sitting on that table were,as it were, Mr. and Mrs. Smiths.另外例句中的第一句能不能写成the responsibility of protecting the environment,as it wre,is with everybody.
3.it is said,据称.是不是前半句无论时态或者主句单复数如何,这里永远不变?One day,it is said,Newton saw an apple fall from a tree.