It depends on the airlines, If they accept to take you onboard. Check with airlines that are looking to travel. Most probably it would be a NO.
You will have to send your passport again for stamping or reach out to IRCC via webform
Just one LOE would be enough for all the sections.
You just need to provide a bank statement with your funds in it. Ideally one account with all the fund and just declare the funds in that account and get a letter from the Bank.
Try to keep things simple,Dont complicate it by adding several...