Questions like this require a review of your file.

It is extremely unlikely that they will be grant non immigrant visas because they have demonstrated immigration intent.

Write to your local office where the ceremony date was scheduled.

Unless you receive a notice/request to mail in the medical you can bring it to the interview. unless you completed your medical after October 1 you...

No. A medical exam is not required for naturalization. You will find a list of requirements at USCIS.gov/N-400

Your lease is a contract. whether you can give 30 days notice depends on the terms of the contract.

You need to check with the requirements of the Canadian government. AVVO is USA law.

Many foreign nationals own homes in the USA and you can also. Whether the bank will give you a loan - probably not but ask the bank.

Yes. As long as you re not employed by the business.

The I-539 and I-539A are directly linked. There is no I-539A without a current I-539.