I do not see how you can get a a waiver for adjustment once you have already been approved. Other than a 237 Waiver in removal proceedings.

It does sound like a mistake. You could contact USCIS to correct it if you wish, or hire a lawyer to do that. it is not clear at all how to do this.

Start now. It can take a long, long time to get scheduled. Yes, you will need a financial sponsor.

There is no set amount of time, it depends on the judge and on the court.

You put the name and address of the employer and the dates you worked.

There is no set attorneys fee. Advertising costs depends on the job and the location.

It was possible many years ago to send one's passport to an office in the U.S. to get a new visa. That has not been possible for at least the last...

There is no rule against it. But common sense may dictate that he would almost certainly file for permanent resident as soon as he arrives, and...

I don't see how you can port to another company for consular processing.

You should contact a Canadian immigration lawyer about that. This site is for US immigration.