Thank you for taking the time to comment. The idea was that the protagonist and his wife come from a normal functioning democratic country. So when Ashcroft admits that they are in fact just tourists, the protagonist assumes that the military will apologize, compensate them, and send them home. Hence the confrontational attitude. At that point, he hasn't fully realized the authoritarian nature of the country.
As for Steam vs. Itch, it's a matter of personal preference. Steam requires you to use a client application, and some people don't like that. But if you already use it, Steam is probably more convenient (automatic updates, achievements, etc.).