Unless your goal is strictly limited to Jōyō kanji learning, you can invest your extra free time in grammar (which is mandatory for language understanding). I find grammar more difficult than kanji learning so far.
Speed wise, one of the best guides on speeding thru WK is here:
I suspect the author was spending more than 4 hours per day most of the journey.
Nothing prevents you from peaking ahead of WK timeline - locked items are still available to learn. You will not get automated reviews, but you may use Self-Study userscript for that (the guide above describes all about userscripts).
Upon reaching 200 reviews per day (which will happen in 3-4 weeks if going full speed), you may not feel that WK is that slow. It’s fast..