I won!
I gathered and cleared everything possible.
I forgot to take the abandoned mine; I just didn't notice it. There are only 14 mummies guarding it.
I had 90 squires – it was a week of alliance right after capturing the territory.
If you know what you're doing, squires are the only dwelling you can take on the map (the hut is inaccessible) that will provide troops. I'm not really counting on diplomacy.
The hero is weak for this hero; he won't gain a single level. It was a waste of time collecting chests for money.
By the way, I have a question: is there an alternative way to complete the scenario, by defeating the Orc and then taking over the garrison?
You can still wait for the "Tomb of Shadows" and risk going that way. There's no monolith exit there; there's a different, more difficult garrison.
Despite the lackluster leveling, with 0 spells, you can still play that way.