You received a check in time which is rarely enforced. Go to the port when you want, rush and get there early and wait for boarding to begin, or go a little later and avoid the wait.
You won’t be able to find out why, you can only speculate. T&C is Carnival owned which probably has something to do with it.
BTW never book a cruise for specific ports they can change and often do and that is for every line.
Curious who you think you could pay extra? The staff works their shift and then they are off, there is no one to pay. My guess is that they are having staffing issues.
Paying on the day the payment is due is fine with NCL. If you use a TA they may require an earlier payment date because they don’t want to be late. If you are working on your own the last day is fine.
The quoted post is nothing more than one person's opinion. You might want to tip someone but saying that you should tip someone is doing nothing more than trying to impose the posters opinion on others. Tip who you want, when you want and the amount you want. Don't let anyone try to push their OPINION on to you.
Usually it is 48 hours to cancel. If you cancel before sailing it will go back to your credit card, if you cancel on the ship the refund will go to your on board account.
The reports indicate that the current variant is more contagious than prior versions, though apparently less serious for most people, qand it is expected to take off, but who knows.