Wellll I didn’t get an answer to my data question, but I tried anyway 
Here you go:
Like I said, it’s not necessarily the same as the “similar Kanji” section on WK, but I hope it’s somewhat useful anyway 
The similar kanji data is from here, WK levels from this post.
The format is a bit messy, but self-explanatory I think:
Kanji (Level): [meanings]
⠀⠀⠀similar Kanji 1 (level): [meanings]
⠀⠀⠀similar Kanji 2 (level): [meanings]
… and so on.
It’s sorted by WK level.