I’ve never taken the JLPT and would probably just scrape by on N4, so take my advice as you want, but here it goes…
Manga is a good source of different fonts though. All the ones I’ve read (not that many) have different fonts depending on the character or context. So if that’s something you’re actually interested in improving on, maybe try some manga and see how it goes.
Also, you can install the Jitai script to change the fonts during WaniKani reviews, though that’ll only help so much since you’re already level 60. If you do try that script, you should install several fonts on your computer so the script can use them.
This should improve with practice, so reading novels is a good idea. If you’re interested, you could try reading 魔女の宅急便, since there are existing book club discussions and vocab lists and you can ask questions there for people who have already read it. Though the fact that it doesn’t use the appropriate kanji may make it not a good choice.
Yes, for stuff I know well. Stuff I used to get stuck on I now read without hesitation. But there’s plenty else that I still second guess myself on, even when I’m pretty sure I know the meaning. So again, it comes down to practice and reading until it becomes second nature.
Have you considered perhaps that you’re rushing a bit? Do you have a reason to pass N1 right now? Because it may be better to study some dedicated vocab and read like crazy for a year and take the test again in July 2019 instead of December 2018.