You seem covered yes, apart from your point 4:
"Arriving at the gate too late (due to item 3 or any other reason): purchase of a new trip"
They actually have this:
"Missed Departure Fee - only available at less than 40 mins before and up to 1 hour after flight departure time." ($159-$170, found on their list of extra charges here), it is so expensive that it is often not worth it, but it does exist.


And for the hand luggage size, I have seen them charge people, but let them board with the luggage after they have paid, so this shouldn't make you miss your flight, and it has been a fast process (less than a minute).

And you can print your boarding passes out up to 2 weeks before the flight, I also always carry 2 copies just in case.