Now if you could remember what it was like to be helpless and face a force so powerful it could erase half the planet, you would know that you’re about to have the exact same impact.

1.这里分不清了：so powerful it could erase half the planet是省略了that的结果状语从句还是形容词的补足语？这个句子中它们是同一个东西吗？

2.然后由上面第一个问题引出了这个问题：Mary was so ill that we had to send Tom for a doctor.这个句子中的结果状语从句的that是否能省略？并且结果状语从句that we had to send Tom for a doctor是不是也可以叫形容词的补足语？

3.you would know中would是虚拟语气，还是表示委婉呢，二者同一种分析吗？