1. Philip bought two tickets for the opera. He was going to / would watch this musical with his friend on the weekend.

2. I was so surprised at the news that David was going to / would play the role of the dinosaur in the play that I gave him a hug out of joy.

3. Lily decided that she was going to / would settle in New York and pursue her dream of becoming an actress.

4. Jim is not here right now. He said he was going to / would be on duty at the library this afternoon.

5. Hey, Timmy. I was going to call you. But now that you are here, I don't have to.

6. The competition was so close that no one was sure who would win the Best Actor award.

请问老师，（1）为什么1-4句中，be going to和would都可以用，但是5只能用be going to而6只能用would？

（2）would是否用在过去时态都是will的过去，而用在现在时态时，除了would like等固定搭配外，都是will的委婉语气？