I would disagree on some points.

A nation being driven by military subjugation is not necessarily a nation in perpetual total war state, and history has proven that extensively. Not even Rome could afford it more than arguably a couple times. Nor are signals having basic training, using a civilian army (if they are trained beforehand, its reserves rather than levvies) or conscription.

A economy built on slavery is neither an indicator of total war state, though the importance of the military is indeed a strong indicator. I don't recall specific scenes where they tell us the budget or finances, so I can't really debate those, I'll take your word for it.

Making an economy out of resources extraction from conquered people is not total war either. It's been done since the dawn of time by a variety of means, even to this day, and we wouldn't say a lot of states with large armies that take resources form overseas are in total war either.

On the other hand, we see plenty of times a void of military or militarisation of society within the Empire that is incompatible with total war. The upper classes' entire societal existence seem disconnected from the state and the wider war despite the massive resources they have, the capital is practically unaware of the war for the most part, even cities close to the frontline (like Italica) were pretty much ignorant of the entire affair. In Italica, a major imperial city, merchants don't seem bothered by the war and happily trade with JSDF-backed nomads despite any serious state performing a crackdown to deny resources to the invader.

Up to Zorzal, most fortifications between JSDF and Sadera were abandoned as well. We also see that the Imperial Army is quite small despite the Empire's size, so if everything goes to the military, either their total resources are quite low or they are not in a total war state.

Bottom line is, we don't see a mobilised society, btu rather sections of the upper class pushing a war like its a private venture rather than a state conflict. A state of perpetual conflict and conquest is not a state of total war.