Modal adverbs

[langga]

Please help me correct these sentences in corect English.

Judy, you should come to school earlier.  You may stay up late every night, but you should be able to control yourself.

He said that we should not come tomorrow because he would/could/will do the work by himself, but he couldn't do that amount of work in a day.

That man must be a new English teacher.  He was being shown around in the school by Ms. Kato.  Well, he might/may be just a guest.

When I was young, I sued to/would play baseball with my father and friends.  My father pitched very fast balls, so I could/would hit them.

I will be a lawyer in the future.  I want to be a lawyer who can help the poor and other socially weak people.

She used to be fat, but now she is too thin.  I think she should/had better/ought to improve her eating habits.