Some things you just have to remember, these sound shifts just show that languages evolve, with the additional challenge that both Japanese and Chinese evolved, and Japanese absorbed both.
I try to add some more information into the reading mnemonic to remember which one is used. So maybe for ぞう there is an elephant involved. For ぼう something is done in a “fat way”, for ほう in a “skinny way” (or maybe “windy way”?). Japanese uses sound symbolisms as well, you just have to come up with one binary thing that you use for everything (also there are pairs like もう, ぼう that are not obvious).
Protip: the component 曽 signified “to pile up”. So you pile up layers 層, pile up earth 増 to increase your earth pile, pile up money 贈, pile up feelings 憎. It actually fits quite well.
Hmmm maybe both, but I think it gets better. Levels 50–60 have some ugly scorn/resent/despise/yearn for parts, though. WK also puts the most widely used things to the front, I had the most trouble with kanji that show up in 50 words, with either multiple meanings in one kanji, or two kanji with a similar meaning. I don’t really remember that this happens again in the same massive scale as it does in the beginning