I mean, it’s totally possible to do in three years imo, so I didn’t even comment xD
I did give some tips to that person who wanted N2 from N4 in 4 months, they might help you too:3 I talked about how much time I spent on things like grammar, listening and reading, so you can have a better perspective of how much time per day you need to spend. Even still, 3 years is a lot and it’s very doable imo.
Vocab was my problem in N2, so make sure to study like 10k on other SRS resource (if you like srs of course). WK is not enough for that, but it gets easier with more kanji you know and you have enough time to finish WK and get done with that 
I have no idea yet about grammar for N1, but after ~N3 grammar is more like a combination of the old grammar points you already know. So getting N4 and then N3 will take you far with getting to read and seeing it in the wild, that helps a lot.
I also agree that the certificate doesn’t really reflect the actual amount of knowledge you have, I barely understood anything on JLPT last time and I still lucked out and passed. Doing more tests and practicing them will surely help you with knowing the questions and getting used to the format.
All in all, I think you can do it, it’s gonna take time for sure, but language is a journey for your whole life, not just a couple of years;) Make sure to have fun with it, read books/manga that you love and want to know more of, listen to the music that you like, watch youtube videos, anime, drama, anything to keep you interested in the language. Have some goals like “I want to play Ace Attorney in Japanese”, or something like that to be motivated along the way. Also motivation can come and go, so have some steady schedule that you can be happy to follow
Good luck, and if you have any questions, be it grammar, vocab, what to read next, which textbook to choose, ask them on the forums and I’m sure there are gonna be some people who can help you 