Short version: Just a quick reminder to not get too caught up in progressing fast on wanikani if it’s to the detriment of your overall learning speed. Ignore if you don’t feel like that’s relevant.
People already seem to have answered your main questions, but I just want to throw in a quick reminder that you probably shouldn’t get too caught up in just studying kanji. Not saying you are, necessarily, but it definitely does seem to happen to people every now and then based on what people say on the forums and I figured it wouldn’t hurt to at least mention it since you sound really focused on the wk stuff. I could be wrong, but then nothing worse than that I wasted a couple of minutes writing this and that you wasted a couple of seconds reading it happened.
So, basically: learning grammar and non-wk vocab is also very important if you want to use what you learn, grammar might even be more useful for actually being able to use Japanese sooner since a lot of easier stuff have furigana, and learning grammar as well also helps with having something to do while waiting for more stuff on wk if you want to go really fast and also learn fast overall and not just progress fast on wanikani.
All just my opinion, though, of course, and what works well for me may or may not work well for everyone else, but I personally don’t regret learning a lot(comparatively speaking, since my wk level isn’t super high) of grammar early-ish since it made it much more possible to actually read stuff
Oh, and I guess I can check the self-study script thing for you, just give me a couple minutes to install it