You should use [Userscript] WaniKani Lesson Filter I think. This script will allow you to do kanji and vocab at the same time. This means you shouldn’t end up with a ton of extra lessons in your backlog, but you’ll level up faster and more consistently than you are now. The average level has 34 kanji and 106 vocab items. This means you want to do three-ish vocab lessons for every one kanji lesson to avoid being left with a ton of lessons in your backlog.
Based on the pace you want to level up in, I think you can do less than 10 lessons per day (you can change your lesson batch size in the WaniKani settings or in the Lesson Filter script itself during lessons to make it a convenient number). For you personally, I’d recommend doing 8 lessons a day - two kanji and six vocab. (I’m not including radicals in the daily count, as I usually recommend just doing them the first time you do lessons after leveling up. But you can work them in another way if you prefer.) If a level has 34 kanji and you do two per day, it’ll take you about 20 days to level up, assuming you do reviews 2-3 times per day and have a good accuracy. Even if you do reviews only 1-2 times per day and make more mistakes than you’d like, you should still level up within a month with this strategy.