I think you're asking a few different questions here. As a free comic you only get one actual genre tag that people can easily filter for, so you're choosing between Fantasy and Drama, basically. I think yours falls much better into Drama at this point.
Then there are your free tags on the series, in which case you should be tagging it as anything closely relevant. Historical, fantasy, historicalfantasy, drama, historicaldrama, characterdrama, political, regency, etc etc. If someone is using the terrible search function at all it means they're probably desperate for something and don't know any other way to find it, so there's no harm in casting as wide a net as possible.
THEN there's your blurb, which is not searchable. So as long as you can fit it into a sentence or two, there's no reason you can't say everything you've just said. "This is a queer, character-driven drama set in real history but with fantasy elements". "An intimate historical drama with fantasy flavor." "Drama, Fantasy, and Intrigue set in an alternate history." etc etc. Plenty short enough for a Twitter post, and has all the relevant information.
Big business wants you to define your product down to the narrowest possible point, but you're not packaging this for big business - you're making an indie comic for people who like indie comics. So I wouldn't worry about paring it down to a 2 or 3 word label. For a lot of people, the fact that it doesn't fit into any one genre is a feature, not a bug, so just be honest and concise and your audience will respond to that.