Good points. I don't know Japanese but when I was learning Chinese, I realized watching shows based in the modern era is much easier than watching "ancient China" shows because the jargon, honorifics, etc. are so different from modern spoken Mandarin. Not sure if Japanese is the same but starting with modern shows and working back to samurai stuff might help.
I'll hear something like 五月雨 (さみだれ) which doesn't have any modern usage and have to remember not to actively study it. Or when older people use something like ねば/ならぬ it's strictly old time language.
I've got to be more casual using short forms, initially the textbooks had me conditioned to polite form. That's how most Japanese shows are, casual unless speaking to an elder. So in that case you would have to remove the casual suffix and replace it with polite.
The amount of times people have told me we don't use that is astounding. But it's not a surprise, in english we don't speak like an account from the bible.
How long have you been learning Chinese?