Level 3 hump help required

For the generic counters and days, in my opinion the only way to learn them is by the power of repetition.
The thing you could actually do to speed this up is for example installing the Self Study script with additional filters and adding a filter like items related to 日 & setting the filtering of levels to 1-3.
Link here

Apart from that, maybe use self-made flashcards for these.

For the japanese keyboard (on Windows) I’ve just enabled japanese in the language settings and then you can switch between keyboards using Alt + Shift and when Japanese is selected Alt + ~ for switching between hiragana/romaji input.