Wow this really looks great, nice classy artstyle, nice attention to detail, you have it down. I'm no programmer but I'm willing to help in any way i can. I've always dreamt about a proper game like this.
With all these characters you should incorporate some 3rd to 1st person mode instead of full isometric, it gives a game more character. And since the player is a detective some kind of inspirations could be taken also be taken from papers please I think.
I don't know what character arc you are taking exactly and it but I'll just add that for a "maximum redpill effect" maybe the player should be somewhat personally "resistant" or maybe even "hesitant", in any case not too sure about what he's actually doing at first and have some lack of understanding before something could happen and an explanation occurs, either in the story himself or by another character as to the meaning of the struggle/National Socialism where he basically gets redpilled, pros if the incident is realistic and tragic enough. The character should also have basic real things such as a home and scenes there. Multiple choices is also important. The characters have to be engaging with the player enough so that what they say is possible to connect combining both relatable truth, jokes, normie and inside humor, humor is extremely important to break the ice in general.
You could also include some animated historical scenes in there, such as the tragedy where Rudolf Hess despite all odds getting on his airplane and flying to britain in attempts to establish peace with the british gets imprisoned/tortured instead even though his cause was heroic and noble the allies wanted no peace.