This seems to have some similarities with Return to Zemia, which is very good but currently stuck in development due to the author’s real life.
The big difference here seems to be that this poor heir is fated to be disliked from the start where in return to Zemia we’re simply a big, blank, “alien” (in practice and culturally, biologically the mc always was alien all along, just a near-human one) canvas.
Will actually read this one when I have a bit more time, maybe over the weekend.
Hahahahahahahah hah! No! Unless you want to end up dead very soon. Monarchs usually tended to be more restricted than rulers who could claim some sort of (democratic) “mandate” from the people.
Monarchs tend to be constrained, invisibly to the larger world perhaps, by a small number of oligarchs whether those people call themselves “nobility” or not. And that is in addition to whatever currents of civil society and delicate social balances they have to navigate.
Rule by (personal) might makes right tends to be reserved to warlords who rule over mostly small and insignificant backwaters and various criminal gangs that tend to disintegrate when the person who held them together dies for a reason. The more sophisticated the system gets the more the ruler tends to have to share power and the more checks and balances there are, even if they only stem from bureaucratic inefficiencies.
That not to say that some rulers cannot have a profound effect and change the course of their nation and history but it usually takes considerable finesse to pull such things off. Not to mention they require a significant amount of buy-in from either the elites or the people, or preferably both. That said the mc here cannot even read so we’re hardly in a position to try for a crown-commons alliance for social change against the elite. 
In any case trying to be a bull in the China shop usually goes badly and even Trump and Johnson can only do what they do because of their perceived mandates and because they have a hard core of enablers in positions of power and influence.
Coming back to it not educating the mc to read and speak and the language was the very stupidest thing our foster parents ever did even if the mc would have lived a normal life and the late empress’ opening to the world had succeeded we could have had a sideline as a translator at least.
Lots of people after all simply like learning languages with no nefarious strings attached and if you’re raised bi or multi-lingual it becomes even less of an issue.
Okay I did play it briefly during my break, but my mc would be inclined to just order Ben to read the entire document out loud to him. Why Ben and not Jessica? Because my mc is convinced he knows the guy well enough to tell if he’s lying.