I hope the author is politically suave, but here's my thinking:
In order to resolve the trading route: I'd say this: I make the road completely free to all, but I make them pay tolls. That means I get people to guard the route, I get income from the trading route, AND I get forewarning if they use the trading route to attack (using the toll collectors as messengers). Not only that, I get to use the trading route as well. I mean, the Holy Order didn't do much to actively fight the orcs, so I get to claim the ownership of the trading route is all mine (since I fight the orcs off). Not only that, I'd gladly let the Holy Order send guards to help protect the trading route. We can share the route and I get to collect tolls. They get the benefit of the road, I have the forewarning of self-defense AND toll income. It's a win-win, and the Holy Order has no reason to refuse or be more greedy, and continuous trade between countries will easily foster amiable relationships within just a century (if we want to become allies). I'm more than confident in my own military might on defense, after all (since we got Dark and a few good Titans).
Even if the MC (dark) is pretty dumb and simplistic, that doesn't mean the worldbuilding is. It's very thorough, to be honest. The comedy makes you underestimate it, though.